Totally understand them not being able to carry multiple people straight away. That can totally be the 15th level feature.
But at 7th level, it’s medium sized. Which, granted, is a wide spectrum. But surely it wouldn’t be too overpowered to allow the ranger conditonally permanent flight at that level, would it?
Exactly. Giant Stature from the Path of the Giant barbarian is the same way. Yet someone casts enlarge person, and it’s +1d4 damage every attack.