I would think what matters is whether or not you’re attempting to form a shared identity that links activity between devices, installs, site visits etc when the user hasn’t explicitly created an account in all of those places. Basically anything that’d allow you to map out their activity regardless of if they have an account or not is what’s problematic.

With some exceptions (such as social media apps) I don’t think it’s generally first party devs who are doing this, but rather third party SDKs that are popular with devs, e.g. Google Analytics, Firebase, Facebook SDK, etc.