The 2004 release was based of a 2K scan of the negative, while the 2019 release is based on a 4K scan done in 2012.
I always thought that the 2004/2011 “HD Branch” was a 1080p scan, as horrifying as that may sound.
The final master was 1080p, but the scan itself was 2K according to someone who worked on it.
Ah, that makes sense.