Online Cheating 2200+

A recent 3/0 blitz opponent of mine with a rating around 2250 played three rather poor games (chess.com accuracy around 70%) and then proceeded to play three absouletly flawless games (chess.com accuracy around 95%).

I'm fairly certain that something was off in the last three games. However I also sometimes play individual games with a +90% accuracy (mostly if I know the theory and convert). So apart from my feeling is there any way to somehow differentiate variance from cheating without any added information (windows opened in browser etc)?

I feel like with the amount of online games played variance is always a reasonable explanation. But this is so incredibly dissatisfying. So since we're in the court of public opionion: Short of 100% proof what would make you believe that someone cheated?