I was still a little concerned due to the previous info I had about "cleaning" and "maintenance" software being unnecessary and potentially dangerous, so I kept prowling around and eventually rediscovered the source (turns out this was not in Apple Support Community after all). It seems that the error was mine (not surprising), in that I conflated App Cleaner and Uninstaller with all of the "maintenance" software on the market. Anyway, for anyone else who may be interested here is what I am referring to and it sounds like the author knows what he is talking about (bolding added by me for emphasis):
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Don't use any of them. The few that aren't straight bloatware trash just do the same basic set of maintenance tasks that macOS does all by itself - further, some of those tasks might look useful but are actually fabulously counter-intuitive and may actually degrade your performance.
Bona fides - I'm a full-time Apple Consultants Network member and have spent the last twenty-five-plus years professionally supporting macOS and Apple technologies in small-to-medium business environments. In that time I have never, ever seen one of these cleaning apps do anything remotely useful whatsoever. I have, however, made a lot of money removing them and undoing the damage they've done when some bright spark decided to install them on a couple of thousand Macs and then watched performance nosedive, hit the ground, and then keep digging.
That aside, I'll give honorable mentions to Onyx (which isn't actively awful) and MalWareBytes (which does a decent job at finding and killing malware that's usually the result of the end user doing nuts and installing every sketchy application/warez/unsupported browser plug-in they can get their hands on).
Apple is a trillion dollar corporation that controls both the hardware and software of their products. They take OS design very, very seriously. These apps push a narrative that they offer improvements on macOS, but the idea that a couple of dozen developers have stumbled on the secret way to make that experience even better is - while compelling - completely baseless.
Tl;dr: Don't install Mac Cleaning software. It's bad and will break things.
Edit: I don't put AppCleaner in the Mac Cleaning Software category. It's an app that removes applications/plug-ins by checking the receipts and finding/removing associated preference files and application bundles. It doesn't position itself as something that will Make Your Mac Better™ - it just does one job, does it well, then gets out of your way.
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Now I have full confidence in AppCleaner and will use it to clean things up so I'll be better positioned for Migration Assistant to do its job.
Thanks again, BDAqua!
