This is a simple toggle in Xcode, right? Data detection for the field, as far as I can tell.

That would be nice indeed. Maybe it'd be even better if they introduced a "phone number" field.

Definitely agree! I often put phone numbers in notes just to have them "clickable".
(so yes, that is a workaround, but it is a bit cumbersome to create notes just for a phone number)

YES.. please do this asap...other apps offer it and it's an essential need of mine

Just incase anyone is looking at this since the new app launched, it's easier to do this since you can add a note at the same time as task creation, e.g.

Call Bob // 02 1234 5678

the "//" creates a note with the phone number, which you can then tap on.

This would really be useful and save allot of time. Most of the competition already offers it.