I think using Android can be either a low income signal or a Grey Tribe [0] cultural signal, and people on dating sites might want to screen out either (or both).

Like you said, it’s about arbitrary norms, but we make assumptions about others all the time based on which norms we follow. An analogy from a different angle is that texting your Tinder match from an Android phone is a bit like applying for a tech job with a @hotmail.com email address.

[0] https://slatestarcodex.com/2014/09/30/i-can-tolerate-anythin...