Could you give some explanation as to how Primeval Awareness is "overpowered?"
I don't consider it overpowered so much as potentially disruptive in an annoying way. I share Dave's DM's concerns. I have not yet experienced it in play, but I do have a player who will be bringing in an 8th or 9th level revised ranger PC next session, so it is a concern of mine.
I happen to know that it has also concerned other people - I refer you to the actual discussion thread for the UA article itself, as there were others who expressed concern about the open-endedness of the ability. I don't like the potential to be "put on the spot" in terms of having to identify the number and location of certain creatures within 5 miles of the ranger.
Getting the ranger player to approach the ability's use with a specific goal in mind would certainly help in that respect. If they've chosen beasts as their favored enemy and they just ping a random wilderness area, I would probably be inclined to tell them simply that they detect any number of creatures all around them. I would bother telling them the number or location of any particular beast unless they specifically asked for bears or boars or whatever. If they wanted to know how many butterflies were around, I'd probably just say there were too many to count.
If they've got dragons as a (greater) favored enemy, and I haven't established if there are any in the area yet, I might say none ... but then if, later on, I decide there is one, I'd have to resort to saying that it was outside of the 5 mile radius at the time. Perhaps it was hunting or something.
Now, I suppose you could argue that I shouldn't put myself in a situation where I don't know what's in the area at least in general. I run an episodic campaign, which generally skips over the traveling through the wilderness segments, so when my ranger player uses this ability, I'll mostly be able to just tell her stuff relevant to the adventure.
It's still something to think about, though.
More specifically, he said that the devs have said that it is overpowered, and that they deliberately made it a little overpowered so that they could see what players complained about and fine tune the overall class based on those complaints. He is saying as much because, as I understand it, Mike Mearls said something along those lines over social media. I haven't seen the statement myself, so I can't speak to the accuracy of the claim.
Mearls and/or Crawford said something to that effect on Twitter. Can't be bothered looking for the quote right now, though.