[swhipple]

They're propertized text. For example, on the splash screen, you can move the point on the logo and M-x describe-char to see that it has:

      display   (image :type svg :file "splash.svg")

https://www.gnu.org/software/emacs/manual/html_node/elisp/Di...

[qwertyuiop924]

That makes sense.

Frankly, Emacs is a fractal of hacks, but it's incredibly powerful, consistent enough from a user perspective, and usually works, so we tend to ignore it.