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

@Akrua 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.