Now a follow-up: The MacBook Pro that I just reinstalled Ventura on was being very cranky about trying to boot normally prior to having done this, and was constantly coming up with a message that the drive was encrypted and a password was needed to open it. No matter what we did, and the password was accepted, we were in a boot loop.
When I got into MacOS Recovery, eventually, as part of reinstalling MacOS we got the same prompt but this time, after giving it the required password, the process proceeded.
After the OS was reinstalled, it's coming up with the classic "Hello" screen, which indicates to me that no trace of the previous account/ownership exists, even if the drive itself has not been wiped. Would this be correct? Or did the drive get wiped because of the peculiarity we were having saying the drive was encrypted and required a password.
Everything I have found regarding the reinstallation of MacOS is that it should have preserved the prior user's account and data if you used the Disk Utility in Recovery to nuke it, but we did not do this. Yet, the behavior of the computer is as that of a "fresh out of the box" Mac, which suggests to me that, at the very least, that someone who's not using forensic disk software to recover data would have no access to anything from the previous owner.
I just can't figure out what has occurred here since we did have the device out of Find My before proceeding, and now that Ventura is reinstalled it's behaving like typical "just out of the box" MacBooks do.