Mounting Shimano Acera Derailleur: Supposed Gap?
I think the yellow landing is for the B tension screw to press against.  That will adjust how hard the derailleur pushes away from the cassette, essentially adjusting the gap when its at the big cog on the cassette.

Small chance that your new derailleur is for a different style of hanger ?

Do you still have the old derailleur to compare?