It’s more complicated than that. In order to get as many devices as possible quickly available to smartthings users, device manufacturers can publish their own integrations that will then appear in the smartthings app.
It’s the manufacturer who is promising the integration will work, and the ones who are doing the actual coding, which is why it was suggested that you get in touch with them. This is a big difference from how things used to work with the classic app.
The “works with SmartThings” program (WWST) is for integrations which have been lab tested and certified by the smartthings staff and which will be supported by the smartthings staff. but that takes a lot longer, so it’s probably only about 20% of the currently available integrations in the new V3 app.
The others are ones which the manufacturers have developed and submitted and are standing behind.