When "Show FPS" is on in Optifine / Options -->Video Settings --> Other, FPS Information is also displayed in the rendered Video
w Replaymod 1.17.1 and newest optifine and optifabric version, could name exact version if relevant
screenshot provided below

wild guess, that will be a wontfix.

This happens wi the simple HUD mod as well

Optifine does not render this text as part of the regular HUD, so this showing in the rendered video is working as intended (in the same way post-processing effects are supposed to show in the rendered video). For this to be fixed, Optifine simply has to render the text as part of the regular HUD (just like e.g. the side scoreboard, the chat or the hotbar).

This happens wi the simple HUD mod as well

Make sure you're not using an old version and then open a separate issue listing the exact versions you're using and where you got them from. I haven't tried it myself but from just looking at the source code this should not happen with that mod.