Missing the 2nd volley wasn't the choke, Im saying the choke was not even trying to win a baseline rally in one of the THREE chances he had when he set up those chances all due to winning baseline rallies. If he felt nervous and played MP differently from a regular point where he found success with a tactic that is exactly what a choke is.
Like I said losing due to an error isn't always a choke. In both FO finals of 2012 and 2014 Djoko it DF because he went for big 2nd serves knowing he needs to establish point control to have a chance vs Nadal on clay. Tossing in a makeable second would likely be a less than 50% chance to win the point and making a big second serve is likely more than 50%. Also Novak wasn't in winning position really in either of those matches since even if he got the serve in and won the point, he'd still only be at deuce and have a long way to go to even win that set, much less the match.
In contrast I think touching the net on a fairly routine volley to lose the 2013 FO SF to Nadal I think you could call a choke and I think Novak played his best match of the three in 2013, so like I said being a choke and playing well don't have to be exclusive.
I do agree Stan did his best and put up a brilliant performance and many would be lucky to push Fed as hard as he did. However, I don't think a great performance and a choke are mutually exclusive and in fact go together because you need to play really well to get into a winning position (the only time a choke is possible).
I rarely like to use the word choke myself as it usually devalues what the opponent had to do to take it away from you, but I think there are cases where it is warranted and this one fits.
Wawrinka outplayed Federer for most of the match and placed himself into a position to win and then ended up costing himself that position by choosing to use a tactic that is not his strongest and giving Fed the chance to answer without having to do anything exceptional. It makes sense to maybe try that on one match point, but to do it 3/3 times especially when each time he GOT match point by winning a baseline rally (twice by winners) seems like a mistake due to a momentary lapse in judgement - i.e. a choke.