I think the important thing being discussed here is devaluing versus penalization. Downranking sites because other sites are serving content/users more effectively isn't a penalization it's a downrank. It's also no different than your desktop site being downranked because someone has built a better performing, better delivering site. Penalization is a completely different animal where your site is removed from SERP's. It really just comes down to creating a good user experience and they aren't going to value a mobile site doing a catch all redirect to a mobile homepage just like they wouldn't carry the same value for a desktop site that gets rebuilt and does a catch all redirect from the old site to the new.
