I’m still learning myself, but I think in a good number of uses cases it qualifies. There are two parts of that explicit definition which seem important, “temporary” and “non-installation”. “Temporary” is the most ambiguous. An array of JBoD storing media files, which can be unplugged really at any time without affecting any system, meets that definition. Game installs or the operating system, less so. I totally get my specific usage may not lend to generic advice. In the interest of me learning, here’s where I started (which advises /mnt): https://perfectmediaserver.com/02-tech-stack/mergerfs/