Same here -- the feature works, and works well.
I can't see a case where a symbol has different footprints for different channels when the schematic is otherwise identical. It really doesn't make any sense.
The problem with having the ability to have a different footprint for the same symbol in this manner is that it is at cross purposes the idea of atomic parts. Remember that a symbol for an atomic part gives the engineer everything needed to describe a design, including the footprint for the layout and a part number for the BOM.
And if you change the footprint for that op-amp, then you've changed the part you need to order, which means the BOM can't be reasonably generated, not without user intervention (which is to be avoided).