Ahh, that might be it. I run TrueNAS too. IMO that should be the default behavior, and you should have to explicitly pass a flag if you want mount to silently mask off part of your filesystem. That seems like almost entirely a tool to shoot yourself in the foot.
I set up a bazzite HTPC specifically because of its immutability and smoother user experience. The steam deck also locks down the package manager because this yields a more predictable environment.