Zardnaar
Legend
Yes but your reply seems to echo the OP with the assumption that the GM is the one changing the rules rather than allowing for the scenario we where the player not knowing those rules for the specific poker variant they were explicitly invited to play. I commented about your metaphor extension because you included a bunch of example rule changes without allowing for the player simply not knowing the rules to the poker variant they were invited to.
The GM does have the right to change the rules. They also have the right to enforce the rules of the specific game they offered to run with a reasonable expectation of not being blamed for changing them when those rules don't match a different game players are more familiar with.
DM kinda has that right but arbitrary inconsistent rules changes are annoying.
Session 0 or based of PC actions are fine not whenever it suits the DMs mood.