If one does purgeAll(A.class, B.class) and that the index metadata is complete and the index contains only A and B (supposedly), we could do an aggressive purge and remove all the data.

But that we have. Well, you would have to make two calls, since purgeAll only takes a single class, but provided the index only contains A and B and you purge them both, I'll expect the index to be empty afterwards.

That could be a global option to enable this aggressive optimization or not.

I am not quite sure what you mean.