That said, I haven't tried this lately, maybe it's gotten more robust over time. But historically, even a bare repo on something like Dropbox has issues.
Sure, but this seams to be more of an issue with Dropbox, not with Git, when I run a database on Dropbox, the same problems occur. I wouldn't trust these to even preserve file attributes correctly, so I would put things into a tarball, before uploading (optionally also encrypting).
Sure, you could view it as Drobox's problem, but the core of it is that git relies on things that Dropbox doesn't support, while jj does not. And so it's usable more safely in more contexts.