I see they are testing this on a Mac. I am curious what the test results look like if the users home directory or even the dot directories are tmpfs. On Linux .bash_login can repopulate dot directories from a archive directory think skeleton files and the dot directories can be ephemeral mounted as tmpfs. The person can have a command to commit their ephemeral directories back to the archive if they want to "keep their changes" so to speak. Or automate it on .bash_logout.
du --max-depth 0 -h -c .cache .config .local
767M .cache
278M .config
2.2M .local
1.1G total
It's really difficult to reliably separate temporary and persistent browser storage. I tried at some point to reduce HDD noise. But given how neither Firefox or Chrome properly follow the XDG spec, it did not yield the results I wanted without a lot of handcrafted mounts.
In the end I'd guess you can also use some aspects of persistent storage to achieve similar results, even if the rest is actually tmpfs/RAM.
Indeed. Apps do always seem to keep adding new cruft to the filesystem layout. For a while my entire home directory was tmpfs on a few machines just to stop some of the tracking. I would commit my bookmarks back to persistent storage but that was it. It was a manual process and sometimes I would forget to commit but that's just my laziness. I'm sure others would automate this process.