Adding new Compatibility to CIQ App

I got a Garmin MARQ II about 3 weeks ago, and have been gently trying to convince developers to update the compatibility of a few key CIQ apps I use. It's my uderstanding (that I'm happy to be corrected on) that as the MARQ II is basically just an Epix in a suit, that this is simply a matter of updating the compatibility rather than any actual recoding.

One private developer responded to my request in 20 minutes, saying that he'd added the MARQ to the compatibility list in his app, recompiled it and resubmitted it to Garmin. Low and behold, a couple of days later it appeared in the store.

However, after finally breaking through the first level customer service of a commercial developer, I've received this response from them:

"While we do integrate with some of Garmin's devices, Garmin controls which devices are updated as compatible."

That seems totally at odds with what the other developer told me. So which is it, how is compatibility defined? I can understand that Garmin might do compatibility testing when app updates are submitted with changed compatibility, especially for new devices, but surely the developer drives this by updating their app in the first place?