The real PowerTOP 1.x (up to 1.2 I think) doesn't use perf events at all, so it is unaffected.
The problem is PowerTOP 1.9x versions, which are actually prereleases (beta) of 2.0, but already shipped by some distros. In my opinion, they should just update to 2.0 since it's a bugfix update over the 1.9x branch.
> It was, however, easier to read the data directly rather than parse the format description, which is why PowerTOP did so
Well, sounds to me like the kernel didn't actually break its promised ABI -- PowerTOP didn't respect the event description so it misused the ABI.