I understand that but you are taking it completely differently. PS5 has an activity card system AND it allows you to leave one game in "quick resume" while on stand-by.
Even Xbox describes the new quick resume option on Series X as an enhancement or improvement to what was there last generation. Microsoft made improvements to it by allowing people to put up to 3 Series X games on suspend and return to any one of them (more if b/c games) and making sure it works from a cold boot. Those are improvements to a system we had in the previous gen on both the PS4/XONE — but only Microsoft tried to upgrade it.
So in conclusion, PS5 does allow you to suspend ONE game at a boss fight and return exactly to that point.
EDIT
Lol. Yes, that's quite obvious and is the key distinction between how the PS5 does it and how the XSX does it. The main thing I am trying to point out to you (regardless of what was already said and how you seem to be understanding it) is that the PS5's activity card system isn't the quick resume option. On the PS5, you can have one game running and set the system into 'rest mode' and come back to that game exactly where you left it and if that is at a boss fight, then that is where you will start back from or you can use the activity cards to go to a specific checkpoint — these are two different options we have. For the rest mode/quick resume option, on the PS5, you just can't start 2 or 3 games and expect to go back to all of them — only the last running game. I cannot make this any clearer.