While this theory might seem somewhat thin at first, it's hard to ignore all of the parallels between Doctor Strange's pose and that of Thanos' on the rock. On top of that, this sort of mockery seems right up Doctor Strange's alley, given his infamous talent for arrogance and self-indulgence.
As intriguing as this theory might be, other fans on Reddit aren't convinced that this parallel was intentional, mainly because Doctor Strange was blipped out of existence between "Infinity War" and "Endgame." "Strange wasn't alive to see Thanos do this," argued u/lyo23. "It's a cool coincidence but never happened." Other users like u/dimlightupstairs and u/Hdog1021 claimed that it only worked because Doctor Strange was brought back to life before Thanos arrived to wait for the Avengers, and that Strange was probably unable to see any of the future that occurred while he was blipped into non-existence. Its worth noting that the film's own storytelling aserts that has Doctor Strange watching the entire future that resulted in their victory over Thanos, hence why he knew that sacrificing himself was the right move. By that logic he ought to have seen the Thanos fiddling with that rock before the final battle, making this flex seem much more plausible.
Regardless of the time-bending logistics behind this moment, if this theory is true, it means that Strange decided to use his last moments alive to mockingly flex on Thanos — making this confrontation on Titan perhaps the funniest scene in the entire movie.
