I didn’t read whole thread and hope I won’t be repeating
Filesystem support is a library (fuse - filesystem in userspace) or some user-level app. It is module in kernel. And no android is not using Linux Kernel per-say, but android is part of Linux Kernel. Android Userland is not part of Linux Kernel, but IMHO implementing filesystem in userland in Android is pointless and counterproductive - it would create more problems, then it would solve.