Yeah, I found that one out the annoying way too.
What's surprising though is that it listed the msstore source as operating normally when I did winget source update. Regardless, kind of crappy this doesn't work out of the box and I have wave dead things not mentioned in any instructions to get this dumb thing working.
WinGet would... launch, but provide no output. And of course, it was my first time trying to use WinGet in general...
A few reboots later suddenly Win+X had Terminal and WinGet started working, and on a subsequent reinstall in a VM I spotted that, yeah, apparently all the extra WinGet, Terminal, etc stuff all has to be pushed from the MS Store instead of Windows Update.
Total pain in the ass.
Ultimately, thinking winget can be used like apt to get a new system up and running is misguided on my part.