This new flow does not send a magic link. It only sends the code. The user stays on the same page, and copy/pastes the code from their email to the signup form. So this new approach does help with in-app browsers (it’s one of the main advantages of the change).
This is certainly something we would like to do next, in the password step of the signup. Apps and websites have ramped up their support of passkeys, I keep seeing the passkeys nudge in many contexts, so it makes sense to add to Discourse as well. (Critical mass of support is very helpful in this switch from passwords to passkeys.)