I have been fiddling with all manner of things to stop this process constantly reopening and starting, and thus far, one thing seems to have stopped it: I shut down MS Word. I had two documents open, one not yet saved, and I suspect that there was some kind of miscommunication between this software trying to save the document in the background, or some memory leak happening, etc. At least the problem has abated - for now.
This tells me, however, that, if MSWord was indeed the cause of the ShortcutBackgroundRunner going crazy, it is not related to the “Shortcuts” app/program entirely, but somehow has problems with this MS software - and potentially any other third-party software that might want to do something in the background.
I can’t say that this is conclusive, but it does give some leads that I hope will prove helpful for me, you, and others grappling with this. If the programmers could just have a look, they would be able to hone in on it much more quickly and easily as they are more familiar with these processes. That is part of the frustration!