In the clip the first part is just the normal song from 2000, and the chorus part is the 'new' version. You can tell because the first part sounds awesome, clear and powerful, whilst the second part sounds muddy, washed out and has protooled vocals.
I honestly don't see the point in rerecording one or every song off Clayman, anniversary or not. It makes no sense to me. A live tour playing the album in its entirety once the CV19 stuff is over? Yeah, that'd be cool. A new song featuring Jesper, Daniel and Peter harkening back to the old Clayman style, maybe even produced by Nordstrom? Fuck yeah, totally down with that (although practically zero chance of that ever happening). Throwing out an unreleased song from the 99/00 era? That'd be sweet.
Rerecording Clayman (album or just the song) in the shitty modern style, though? No thanks. I prefer to keep Classic IF (1994-2000) completely separate from Nu In Flames (2002 onwards) - and it's not like I hate everything post-2002. I like a lot of it - but it's still a completely different era to me and not one I want mixed with the classic period. I can deal with it when it comes to live performances but that's my limit.