Another possibility, and I'm not a coder so...take it with a grain of salt.
It could be that Peloton simply doesn't want to support a subset of their equipment with an Apple only piece of tech (gymkit). I don't pretend to know the app differences, or what coding is necessary in Peloton's back end to know that I used gymkit over the Peloton app, but streamlining things from the developer side (everyone uses the Peloton app now, we are deprecating GymKit going forward) would make things more simple from their viewpoint.
It could be that Peloton simply doesn't want to support a subset of their equipment with an Apple only piece of tech (gymkit). I don't pretend to know the app differences, or what coding is necessary in Peloton's back end to know that I used gymkit over the Peloton app, but streamlining things from the developer side (everyone uses the Peloton app now, we are deprecating GymKit going forward) would make things more simple from their viewpoint.