I know, but I'm lazy and I'd like to be able to know by looking at a link instead of tapping and holding each number for a few seconds (and then pressing the cancel button if it's a phone number).
Apple could put a little phone icon to the left or right of the auto-generated links. In my usage though phone numbers are very rarely linked (where would they go?), so when I see a linked one on an iOS device I assume it will trigger a phone call.