I don't know the specifics about what or where his ankle fracture was, but it isn't uncommon for an athlete (especially a highly skilled, trained athlete like Waddle) to come back from an ankle fracture 4-6 weeks after injury depending on what and where the fracture was at, and he's had that much time and more. If he fractured the non-weight bearing fibula, I have had HS athletes return in 4-5 weeks without any performance issues, and I'm sure Waddle is getting better rehab and more attention than an 18 year old female soccer player in HS.
Surprisingly, bone heals a lot quicker than some of the soft-tissue and ligamentous injuries that often hamper an athletes ability to return to 100% quickly. To your point about just starting land running. That is the more important aspect of this, and with the muscle atrophy that occurs with significant lay-off, it would be very unlikely that he be @ or near 100% if he is available next week. But a Waddle at 85% is still an additional weapon that the Bucks DB's would need to account for and Bama has plenty. Just like OSU's youngsters, just bc people have not heard of them doesn't mean they can't play.