[mwt]

Your explanation doesn't really distinguish high-level human play (not obvious cheating) from engine play (obvious cheating). There are probably plenty of games in which your first 20 moves (or 5-10 for me) are in GM databases and evaluated favorably by the engine, ass a 2200 you're probably booked up pretty well. But you know computer moves aren't so common in openings; they're much more common in complex middlegames and late games when the computer can calculate more combinations that we can and is able to produce lines that break intuition and principles but are strictly best.

[toolslive]

My point is that high level human play online can be caused by computer analysis offline. One cannot observe a difference, as the moves are exactly the same.

[mwt]

But for the vast majority of players there will be a difference in computer lines and human evaluation; even if you're playing a strong game there is still a world of difference between 2500 lichess and ~3300 FIDE stockfish. This is more true for the median ~1500 lichess player. Even if you put two GMs up against each other and give one a computer, some portion of games would include an obvious computer line that a ~2800 FIDE human wouldn't evaluate the same way as an engine.