You can gain cap space next year by extending him, rather than picking up the extension. It does make sense. The guy has improved a lot every year, and is just now coming into his prime (the usual for interior Dlinemen). What doesn't make sense is letting a top 5 player at his position walk for nothing.
Everybody knows he is an excellent player. Luckily the Dolphins have him under contract for 10 mil in 2023 and do not have to do anything. They should always wait and not run to resign players. But more than that, for any DL, at the the end of 2023 if it comes to resigning or cap, cap should take precedence, he is not that important to resign.