There seems to be a conceptual problem with face recognition and cropping. Lightroom detects faces in areas that are not visible according to the cropping. Since the detected people go into the keywords, this may cause problems later (Hey, I was on this image and you cropped me out? Hey, why does google find this image with my name tagged but I am not on it?).
Should I report this as a bug or is it a feature?
PS: If this was a bug and fixed in future releases this would be really cool because then face recognition adds value. If I tag my pictures without face recognition and then recrop, I would have to adjust the keywords manually. With face recognition this could be done automatically. Great!
You can report it as a "problem" at the official Adobe feedback forum: Recently active topics in Photoshop Family about Photoshop Lightroom
Don't worry about the semantics of "bug" versus "feature request" -- just focus on what the current behavior is and what you think the behavior should be.