I think the bulk of it was a link from this site:
(these sites also have examples):
https://www.themarysue.com/remastered-buffy-is-a-butt/
https://gizmodo.com/oh-dear-buffys-hd-makeover-is-a-total-mess-1671812347

As far as I can tell, Joss Whedon is very opposed to it being released in this state, and these been no traction in the last few years for this coming to home media (all the streaming sites still use the original SD masters too). I’m not even sure if it still airs on HDTV like this anymore, or if it got recalled.

If you really wanted to, you could track down the HDTV airings, and then recreate the original framing of the show by cropping and re color-timing the open matte shots and discarding the cropped shots for SD footage (which are probably numerous, eps. the SFX shots). Probably not worth the effort.