now its just the comparator with a piece of redstone in front and it works reliably by having the lever off, updating the bottom dispenser and then turning the lever on.
Remove the piece of redstone in front of the comparator and it does not update.
My guess is something game tick related?
Still when updating by placing a block after about a second or so, nothing happens.
WHEN the comparator is there i cannot prime it. If not i can.
Meaning this would be MC-108 but that the comparator can override MC-108 from actually occuring after about a second or so, and also that then a redstone dust one block over can make it occur even if not even pointing at the dropper.

omg i keep going:
the dust does update it immediately. While a repeater does not.

I CAN prime it with the comparator in front.
what I did was try cause block updates by putting the item in and out so the comparator changes state.

THIS does not update the block for MC-108.

THESE are what is happening and im assuming the comparator non-block updating is intentional.
The dust update distance i do not understand, sorry for the spam...