Guitar tuned down half step for Buddy Holly

Hey everyone - beginner question

I'm trying to learn Buddy Holly by Weezer. While watching a tutorial it says the lead guitar is tuned down a half step from standard tuning. But rather than tuning the guitar down a half step can you just play each chord or note a half step lower? like for example rather than tuning the guitar down a half step so a power chord at the second fret is an F chord rather than F#, couldn't you just play an F power chord at the first fret in standard tuning?

I looked up the tab and it's got a couple strings played open on a couple riffs. You can't get lower than an an open E unless you're tuned down a half step. That might be for part of the song you're not learning so it might not be important but according to the first tab I read you have go be tuned a half step down to play the whole song.

EDIT: misspelled tuned