The best day argument is entirely subjective and needs a shovel of nuance. It doesn't take into account the condition of the top players in that match, and it doesn't give any significance to the overall win rate against the top players.
For example if Player A has a 4/30 win rate against ML/FZD/XX, but has at least one win against the trio. I don't think saying he can beat them on "his best day" is a good measure of player A's ability, more like he can beat them when they have their worst days, when heaven and earth align, and the creeks don't rise.
But a 30% win rate against the top players definitely warrants a "can beat them on his best day".
We just have different parameters for how we assess players and also what tier they belong to.
It is all subjective and that why discussion is needed and usually that involves recognising the points of agreement on both sides (as I've done in reference to past results) but there is no attempt to assess the player right now and the collective results of the past 6 years because that doesn't fit the subjective narrative.
All we can do is wait, and if he takes down a few more top Chinese then I'm wrong and if he doesn't then I'm wrong because, well, you know, years ago and we'll just keep saying he's comparable to FZD and ML.
I had a similar(ISH) argument about Gauzy before where I was trying to say I've seen him play so well and look like he was going to pull a result, like where he looked like a threat and superior players had to up their game to beat him. He beat XX in 2019 and expectations for future results were there but they never happened. He'd go 1-0 up and lose, 2-1 up and lose etc. Have a game point at 10-9 and miss it etc and I was laughed out of here because Gauzy is a pretender and a joker apparently.
And maybe he is but he can play in a way sometimes that makes him a danger but I never classed him as a real threat or compared him with FZD or ML.
I'll go out in a limb and guess Gauzy has a better H2H V LSS and that LSS was beating him 6 yrs ago and Gauzy has better record in recent yrs but memory only, could be they're tied on H2H...?
Anyway, I'm flogging a dead horse so I'll take my assertions about tiers, levels and threats and keep them for training hall discussion, it's not constructive discussion in here