So, I think I am having some indications about how 'optimized battery charge' of monterey works.
I keep a pattern of leaving mbp to drop its battery charge around 80%.
Then, I plug power again.
I keep this pattern about 3 weeks now.
So, I noticed, that it no longer charges battery at once.
Instead, it charges it from 80 to approximately 90%,
and then it stops charging about an hour.
Then it proceeds and charges battery to full 100%.
Again, I am not completely sure that it is 'optimized battery charge' of monterey or something else,
but I think that mac handles this charge in its own, possibly better way.