I can't confirm this. when using vi, I have syntax highlighting, split windows and even search and replace. Even my Termux installation states it's vi improved, when issuing vi -h.
That's what I'm trying to say - in the probably most upsetting way - All of my distros - Ubuntu, Nobara, Debian and so on: all of them have vi as a symlink - only, these days.
Not all! My arch Linux install definitely has the original vi -- the one where when you cw it doesn't delete the word until you go back to normal mode to save on screen refresh. Plugins? Custom commands? Multiple buffers? Forget it!