I know that the FDS is Japanese but for D-4 Any% and D-4 Warpless, why do people use the Japanese version?

For Lost Levels Warpless, there are no meaningful differences between Japanese and North American. S&Q is 73 ( I think) frames faster on J, but last I checked, those frames were removed from final time for any% D-4 runs on US carts/rom. People who run other games on SMAS like the J-cart, specifically the J 1.0 cart, for faster reasons in those other games.

Okay Thanks!

Also resets are slightly slower in general.

They use the Japanese version because you can grab the flagpole backwards and it saves some frames

@AkruaAkrua it saves a framerule

In Lost Levels, you can manually jump backwards at all of the flagpoles in both NTSC regions. The 'backwards pole grab' region difference applies to SMB1.