Caro Kann: Panov Botvinnik attack question

Hello all,

I have been studying and restudying and implementing and adjusting and rereading and practicing via chessbook.com Jovana Houska's Opening Repertoire: the Caro-Kann (Everyman Chess) for around a year now.
The chapters on the Panov-Botvinnik always feel like new material to me, because it is so different from the rest (this is not a bad thing I still love it). More importantly, and more impactfully, at my level those games are rather few and far between. When they come up and I kill it it feels wonderful to have been prepared. But when it comes up and I don't kill it it is painfully clear I do not understand some basic though processes.

Recently I had a game that was some sort of super odd Panov where white seemed to not know what they were doing and followed the usual opening moves with Be2. I paused and thought "Wait. So there is no reason for me to prep Bf5 with g6 AND I get to have my opponent's bishop on a more passive square... for FREE? SIGN ME UP." and basically played a positionally improved Panov from the black side while ALSO being up a tempo after just sending it to Bf5.

Which leads me to my question.

Why, after

do we not just pin the night as-per-usual with Bg4? If there is a repertoire-specific reason specific to the book I absolutely respect that (I'm learning a lot the past year about consolidating to a less-than-optimal repertoire that is actually better than an optimal repertoire because you can ACTUALLY UNDERSTAND IT) <--this only took me 20 years to appreciate.
If there is not a repertoire-specific reason... what is that reason?
Thank you kindly for your insights!

edit: to be clear the diagram is not my game. That is the book position that is the root of my question.

edit2: Oh. Yes I won that game handily

Bg4 is the most played move at master level, and the top engine move. It's a very theoretical position so maybe that's why your author wanted to avoid it... I'm only speculating, there's really no telling what your author had in mind, you'd have to either read it in the book or ask them to know.

I mean the book is from 2015, but it is still a very respected work on this opening on these forums and others. Further it most certainly was still the top engine eval in 2015. I understand that Bg4 is the top engine move, it was one of the reasons I have this question. I'm not interested so much in pure engine evaluation though. I want to know and understand the 'why'. Are there super sharp engine lines you must memorize to play that correctly as a human? Are there super sharp non-engine lines that you must learn as a human that are simply not practical for a US local-rated 15xx player to maintain in their repertoire?

i.e the reason that in certain advance variations she has the student exchange with c5xd4 --> c3xd4 before Bg4 pinning the knight, because there is a specific line that white can choose after an immediate pin that is just too ridiculous and sharp to expect a casual to learn.

edit: You kind of answered my question with 'its a very theoretical position'. That is likely the reason then. I still am curious as to specifically why though xD. Thank you

The Bg4 line leads almost by force to an endgame that is very drawish. "Keep it Simple for Black" suggests 6...a6. Botvinnik's 6Bg5 might be ambitious try for white.