It's not about multiple equilibria but about (often unintended) collusion.
Examples of that affecting poker games are very well known. One frequently occurring example was discussed in online community 15-20 years ago (BTN raises in a limit Holdem game, SB calls too much which hurts both the SB and the button giving equity to BB).
I don't think you're correct saying it doesn't affect poker as people were able to notice and analyze this before solvers. It's true though that no-limit Holdem as played today (two blinds,no ante,deep stacks) is likely not strongly affected by the phenomena. I don't agree Pluribus experiment shows much when it comes up practical play. Not enough variety of skill levels, not enough hands and not enough time for metagame (people adjusting to how others play) to develop. I do agree pure equilibrium play is most likely not terrible in cash game nlhe but definitely not in poker in general.
I don't think you're correct saying it doesn't affect poker as people were able to notice and analyze this before solvers. It's true though that no-limit Holdem as played today (two blinds,no ante,deep stacks) is likely not strongly affected by the phenomena. I don't agree Pluribus experiment shows much when it comes up practical play. Not enough variety of skill levels, not enough hands and not enough time for metagame (people adjusting to how others play) to develop. I do agree pure equilibrium play is most likely not terrible in cash game nlhe but definitely not in poker in general.