LGTM. I agree with Matt that it would be great not to create those other pressure sets in the first place, possibly by adding some .td file construct to explicitly list the ones that are required. That said, this change is clearly a step in the right direction.
We need only 2 or maybe 3 of psets, and this makes a lot of sense to add a syntax to explicitly request psets, but even then we need an enum to identify these 2 or 3. I.e. I agree as well, but the change is orthogonal.