Shouldn’t you set it about 1/4” below whatever you’re cutting?

The treatment generally goes into the wood only few centimeters so in some cases the cut ends do need to be treated. I've replaced pieces of deck framing in the past that had rotted out because this wasn't taken into consideration.

This is under a roof so it doesn't get wet regularly. However even if it did that would be okay due to the NTR-AB grade treatment on the wood. It resists water for as long as it gets to dry out in between. For framing I use NTR-A grade which can withstand being constantly wet but there the cut ends needs to be treated or else that's where the water gets in and it'll rot from the inside out since pressure treatment is only on the surface.

I can't say for sure from pictures but my guess is everything is safe for in water use and so no worry. It doesn't take much to drain the water out

I think that’s what the problem with the existing deck was lol. Also no-one uses hardwood cos it costs so much more.

End cuts trapped behind fascia can retain water if they’re not completely sealed off from it getting in there in the first place. Better to treat your ends before covering them because even if you do it perfectly now, the deck can get worn or damaged later and allow water intrusion. Lasting builds design for reasonable fault tolerances.