Alright I woke up today finally remembering how this all works.
@legendaryan was of course right - last year teams could not cut players after the last day of the season without intervention from the commissioner.
This has been true for many years - after 11:59pm ET of the day the MLB regular season ends, cuts are locked until after arbitration. Or at least, cuts should be cut off.
During arbitration, cuts are not allowed because unwinding arb or votes for cut players is too complicated to really force people to engage with.
Before arbitration and after the regular season ends (the period of time in question), the reason was simply at some point the system will do year end stuff and while salary increases are applied, etc, any cuts will mess up the system.
So, to answer the original question correctly:
Teams cannot cut players from 12:00am ET the day after the MLB regular season ends until 11:59pm ET on November 14 (the last day of arbitration). Teams can also not cut players from 12:00am ET on February 1 (the keeper deadline) until the completion of their league’s auction draft.
This makes the related question about illegal rosters both more of a pain and more enforceable from a league’s perspective. I stand by my advice there, but now as a league you know that people cannot cut penalty-free immediately after the end of the regular season, which may mitigate some “bidding practices that go against the spirit of the game” to quote @legendaryan
I’m documenting all this so future Niv doesn’t forget why this stuff works the way it does! And to inform any commissioners grappling with this question.