The generic domain interpolation algorithms didn't quite work for selections. The interpolation would do unexpected things that were different than the results in edit mode. The new behavior is supposed to be the same as edit mode, although we also have to handle face corner selections here. Currently the code assumes that all boolean attributes should be handled that way. I'm not sure of why that wouldn't be the case, but if we ever need non-selection boolean attributes, that could be supported too. Differential Revision: https://developer.blender.org/D12488