No-one ever seems to consider the possibility that the general public are pretty rubbish at identifying actors, and misidentify them half the time. There's loads of pictures out there of people with 'celebs' that are actually just random people that look vaguely like someone famous. And every famous actor will tell you stories of being mistaken for a different famous actor.
I bet at least some of these THEO 'sightings' are nothing of the sort! I can well believe that someone mistook blonde, petite Brie Larson for blonde, petite Elizabeth Olsen.
As for date-like horse-riding with Scarlett - well, his response at 3.20 ish in this interview is pretty definite:
https://www.youtube.com/watch?v=XgoAbjwLfVs
rolls eyes 'You can go as friends as well...'
Happy New Year to all....