I agree with Maximillian; there’s a notable distinction between a free prototype that later becomes a full instrument and an intentionally feature-gutted demo version posted at the same time as, and with a link to, the full version of the library. Neither the Air nor the Kawai Felt pianos link to or even name the full instrument they represent in the written copy. Furthermore, Spitfire (obviously) and Jon Meyer both have a history of freely available instruments on the site, which reads very differently than an account whose first instrument is like a press release, yknow?
Though I can see the other side of the argument too — that functionally, if you ignore the existence of the commercial counterpart, an ocarina with an intentionally limited sample pool is no different than one with limited samples because that’s all the creator happened to record. If Pianobook is meant to be just a resource for a lot of free, functional instruments (e.g. no developer-scripted timeouts or other limitations that impede playing), then maybe the more the merrier.
The concern seems to be more in “opening the floodgates” for other commercial developers to use the site as a classifieds section. Sharing a demo instrument on Pianobook as part of a sales funnel is a bit at odds with the spirit of the site, which seems to be “people sampling interesting things they find, learning how to make instruments, and sharing them for fun.”