With regards to his recent rating increase, Hans' rating increase is not completely unprecedented but it's still very rare. The issue isn't that he's a mid-2600s player, or even that he's increased by 200 points in two years, it's the shape of the ratings graph and the unusual staircase progress he's made at the GM level.

It took Hans about five years to go from 2300 to 2500 rating, and most of that was pre-pandemic. Increasing your rating gets exponentially more difficult as your rating increases, which is why there are so few players who ever make it to the 2700 level or even the 2600 level. Most players at this level who spend multiple years in a rating lull never significantly increase their playing ability (there are countless examples, but look at someone like MVL for a typical example). There are only a small number of cases of people who reach Hans' level who have staircase looking ratings progress graphs at the 2500+ level.

Hans' recent rating increase is far from proof that he's cheating, but it is definitely extremely unusual.