I'm not sure if it was ever based on anything other than anecdotal evidence or observation bias, but the thinking went something like this: The away team would be conservative because the first leg was really only the first half of a match lasting 180 minutes, and the home team would be terrified of conceding that "all-important away goal" (another trope).

Whatever the case, this Champions League season was different. And it's not just about the number of goals scored -- 20 over four semifinal games -- but rather the way the ties unfolded.

Nobody parked the bus. Everybody spent most of their 180 minutes either playing on the front foot or trying to win the ball back so they could attack. When teams took the lead, it didn't seem to occur to them to manage the advantage in the traditional way: making the pitch big by spreading the passes around, controlling the tempo, dropping the team's centre of gravity so as to suck them forward and create space behind. And when they tried, they often came up short.

Most of all, these four games were marked by mistakes. Plenty of them.

You had tactical ones, like Roma's absurd high line against Liverpool's roadrunners, which turned Federico Fazio and Juan Jesus into twin Wile E. Coyotes, or Real Madrid's pigheaded insistence upon trying to play through the Bayern press each and every time.

You had technical ones; too many to count, so let's just name those who made the most egregious missteps on the defensive end (one per team, to be equal): Radja Nainggolan, Sergio Ramos, Dejan Lovren and Sven Ulreich.

You also had poor finishing. Lots of it. The result, for those who like their expected goals, are xG maps that look like this and this.

That is a ton. And we might have had even more if not for some distinctly disjointed refereeing, from unseen handballs to -- for me anyway -- the biggest blown call of all: Ramos' bodycheck that sent Robert Lewandowski flying.

Expect think pieces about the "lost art of defending" in 3, 2, 1, but perhaps it's a little bit simpler than that and, maybe, drawing massive conclusions based on four matches is premature.

There are plenty of other reasons for what we saw. These four teams might have reached the final four, but there's a reason three of them are third in their respective leagues and the fourth, Bayern, have a 24-point lead at the top and haven't really had to break a sweat too often since February.

These are imperfect entities; three of them simply do not suffocate opponents and kill games consistently, while Bayern, which probably could, have elected to spend the past three months chopping and changing personnel, losing chemistry and edge in the process.

All of that leads to mistakes, and so too does in-house philosophy.

Jurgen Klopp -- by choice -- is an attacking manager. So is Zinedine Zidane, though perhaps less by choice. Jupp Heynckes, who knew he was retiring (again) at the end of the campaign, restored Bayern to the Guardiola Era mindset: two wingers and a centre-forward, plus James Rodriguez and Thomas Muller.

And Eusebio Di Francesco, while perhaps not as obsessively attack-oriented, is nevertheless one of the most daring, roll-of-the-dice coaches out there, a manager whose style adheres to the Kenny Rogers credo: "Every hand's a winner/And every hand's a loser/ And the best that you can hope for/ Is to die in your sleep."

Press high up the pitch and you force mistakes while exposing your defence; it's as simple as that. There's always a trade-off in football. These teams can beat you in different ways, but what really gees them up is luring opponents into areas where they can hunt the ball down and then, with one or two passes, shoot on goal.

It's true that, broadly speaking, there are more teams across Europe looking to play attacking football and defending higher up the pitch. But there are also some who view it differently. Replace these four semifinalists with, say, Juventus, Atletico Madrid, Manchester United and Borussia Monchengladbach, and maybe our experience would have been distinctly different despite the fact that, as a group, these four aren't far worse than the other four (and some might say they're even better).

In fact, that probably also explains the lost art of defending narrative. Sure, there aren't many Paolo Maldinis around, but there weren't too many when he was in his prime, either. Defending is a whole lot easier when you're 30 yards away from your goalkeeper, your full-backs are actual defenders and not recycled wingers, there are two holding midfielders protecting you and you don't have a bunch of wild-eyed forwards hunting you down every time you have possession.

Throw in the fact that every defensive error is scrutinized like never before and you can see why defenders so often are treated like cannon fodder. (Not to mention that the good things they do often involve the sort of stuff that doesn't make for good highlights.)

Put all this together and maybe these semifinals weren't the chaos that they appeared. In fact, unless you're a Bayern or Roma fan -- in which case you're wondering what might have been and how you didn't overcome far-from-unbeatable opponents -- you probably enjoyed these games.

There were gross mistakes -- yes, from referees, too -- but there were also moments of wonderful skill and two ties that remained in doubt until the very end (OK, in Roma's case, the last five seconds, but still).

Mistakes are part of the game, and error-strewed ties do not mean the sky is falling. More likely, they're a one-off. And a welcome, fun one at that.