I forgot the upgrade planner could downgrade, but yes that's working as expected for me. Only single entity ghost replace is doing this.

When downgrading a level 2 or 3 assembler by placing a ghost assembler 1 on it (either remote view or holding shift) the recipe is always cleared when a construction bot does the swap.

I would expect the recipe to be kept as long as it is valid in a level 1 assembler, which is what happens when you ...