For example, let's say I want to use a Fitbit. I download the app, enter my real height and weight, but I give a masked email, fake name, fake birthday, etc. I always use the app with a VPN.

When doing an outdoor activity, I would allow my precise location on a run.

Is there really much of a privacy risk if they don't know who I am?

Please don't just suggest Gadgetbridge or a similar alternative.