Lower? Probably
As far lower as 820? More likely no than yes. But perhaps.
As far lower as 780? Quite unlikely we think
One way to think of this is to take someone with a lot of games who is a little under 800 [e.g., John Morra, 794, 22,000 games] and interrogate John's record to see whether his performance for a hot string of 500 games ever pings near 840 or 850. He has 44 of these 500-game chunks, and we might imagine there is one chunk for which he was playing his own A-game, tended to get the rolls, and his opponents tended off their game on average. That's the trifecta of high apparent performance. While John sees 800 about 30% of the time, he never sees 820. 819 (25 above his rating) is as high as it gets.
If Ameer's 500 game chunk that we happened to capture is the equivalent of John Morra's best chunk, that would suggest Ameer's long-term average to be 824 or so. It is more likely he is somewhat above that, though.