Those after game ratings are not reliable at all.
They are based on the starting ratings that are put in. After you run a game review, you can change the ratings of the players being reviewed (change them in the pgn) and it will directly change the resulting rating estimate-- So a game rated as "2350" played by a 2000 will be an "1850" game played by a 1500 and so on..
Are Lichess rating getting more accurate?
So, today I played this game on Lichess against a 2004 rated player and he didn't play like a Lichess 2000, Chesscom game review says, he played like a 2350. https://lichess.org/z9NGrwQd/black
Previously a 2000 there was like a 1700-1800 on Chesscom but now every opponent I face there plays true to their rating or even better.