Thank you @Krzysztof.N ! Worked as expected. I will try to make a repro scene for you, during next weeks.
A side question, please: does it have sense to ask if are you considering something like stochastic (Megalights) for RT AO? All lights are now Megalights, but only if using short RT AO we will still need to use Nanite Mode 1.
BTW, I also noticed a little discrepancy in RT AO:
5.3:
5.6:
(Ignore the blueish layer I added in 5.3, as colors were warmer in that version)
In 5.3 looks more fine and detailed. But in both versions look like missing some darkness under the cushions, isn’t it?