We can't, at least not without a platform change. This overrides the base implementation of get_unit_key that raises NotImplementedError if it's not overridden. The rationale at the time was that you'd never want to actually omit the unit key.

I'm still fuzzy on if I think that's correct. We clearly have an example here where that's not the case, but I still kinda like the idea of pushing that model. I ended up 50/50 in my internal debate so opted to leave it as is for simplicity.