I would argue that these players in your example don't know the chords to the song, which exactly proves my point: that it is of primal importance to do your homework and learn the song.
A player who knows zero theory, but actually knows how the song goes, would have given the superior performance in that situation, is my point. The musicians in your example should have spend more practice time, just learning the songs.
So the perspective I’m coming from here is of someone who routinely plays songs I don’t know in a live setting.
I play bass at church, and frankly the music isn’t what I’d choose to listen to on my own. Rehearsal is tonight, and I just got word yesterday around dinner time that the set list is finalized. I think two of the songs I haven’t heard before. Maybe it’s only one, and the other I just forgot about. Who knows.
I’ll take about 30-45 minutes at some point today to look at the songs, do a couple of play throughs. Biggest part is knowing when the bass comes in and drops out. Since most of the songs seem to have bass parts written by guitar players, I could just play roots and call it a day...but that’s boring, so instead, I’ll come up with some bassline ideas that fit the song, and are as involved as possible, trying to stop just shy of the mark where it triggers “can you just play the chord name, and try to only play notes when the bass drum plays?”
I know the other folks on rotation for the bass do NOT do that. I can listen to the livestreams where I played, and as long as I make sure to dial in the DI pedal, you can tell there’s a bass guitar part being played - not overly standing out, but there to be heard if you choose to focus on it. In contrast, I find it almost impossible to hear the other folks when they take a turn, because they’re following the chord chart and only the chord chart. There are no 3rds, 5ths, 7ths, passing tones, etc. unless you see an inversion specified. There’s no walking up or down. There are no octave leaps.
They clearly “know” the music - in fact, they likely listen to it. They start and stop at the right times. No note appears out of place.
This is what knowing the theory does. It allows you to parachute in, and go for it...or if the arrangement changes, you can quickly adapt.
I once played a church set on an Irish Bouzouki. It’s basically like a Mandolin, but an octave lower. Initially was just going to play chords, but was told that it was cutting through too much, so they asked me to play single note stuff. This was about 1.5 hours before I’d be playing the instrument live...an instrument I had literally just bought a few weeks prior. Without a decent grasp on theory, I’d have been sunk, but instead I borrowed a little bit of theory and approached it like the soft beginning of a late 80’s/early 90’s thrash metal song and came up with some cool ostinati.
Knowing and understanding the “why” does remove some of the mystery and magic of it all, but then again, so does watching that YouTube video where they demonstrate that every song is Pachelbel’s Canon in D.