Personally I both agree and disagree with you. No team ever goes into the game thinking "alright, we're gonna concede 1st, 2nd, 3rd baron", and the fact that G2 did, was the result (like you said) of either their mistakes that they shouldn't have made, or good play from SKT.
However, while you're saying that G2 was good at thinking on their feet, and was having good responses to what SKT was doing, you're phrasing it in a way, that makes it seem like G2 players were forced to make something happen so they don't concede the map completely, and the reason for it working out was purely good execution - and that's where I disagree.
We've all seen what happens between 15-25 minutes when G2 don't do those mistakes - they snowball out of control and close out games extremely fast and efficiently. The reason for that aren't godly mechanics from all of their players (that's not to say they don't have amazing mechanics, because they do), but the way they prepare the map beforehand.
In those games they didn't acrue leads like they usually do, but they did play the map the same way, pressuring multiple lanes, forcing SKT to react in some way to what they were doing. And even when falling behind, the state of the map allowed them to negate advantages SKT had. G2 played the map much better than SKT, and if it was actually G2 winning those early games, then they probably would've snowballed like they usually do. Instead they had to settle for negating what SKT was doing, but it was only possible due to better fundamentals and macro from G2.
The real discussion here should be, if the mistakes G2 and SKT commited during those games are weighted correctly, do 2 mistakes from G2 have the same implication as 1 mistake from SKT? At least as far as baron goes, if a team that secures it in fact LOSES the pressure on the map, then - to me at least - it's a much bigger issue, than a player getting caught out which leads to an enemy team getting that baron. And like you said, SKT didn't utilize baron well in the series, or even pre Worlds. I'm certain, that G2's coaching staff was aware of that as well, and they knew how to attack SKT in the event they secure baron.
Like I said, no team goes into the game with the idea of conceding baron, but if you've got a good plan on how to deal with it in case it happens and are able to execute it properly, while the enemy team has no good response to what you're doing, then to me the team with better plan and execution is the one playing better, at least in that part of the game. SKT had definitelly better early, while G2 (to me) had better mid and late game. So it really depends what you value more in this case, but dropping hypotheticals (had SKT gotten G2's draft, had they snowballed better, had they executed this or that teamfight better) just sounds like a bit of a cop-out to me, because in the end they didn't do any of those things. And the game to me starts in draft phase, and that also should be taken into account.