MORE weird behaviour. I deleted the Shared Folders via GUI and unmounted again, then did the lazy umount of /dev/sda6 and listed directory contents of /srv. Showed the AppData and ServerFiles folders and no dev-disk-by-uuid-6919b6e7-2b51-4384-b2e6-67b8109762d4 directory. cd'd into AppData, cd'd back out of it and into /srv again, listed directory contents again, and this time AppData and ServerFiles were magically gone, and it started showing dev-disk-by-uuid-6919b6e7-2b51-4384-b2e6-67b8109762d4 directory. Checked for hidden files, and same thing. So I removed dev-disk-by-uuid-6919b6e7-2b51-4384-b2e6-67b8109762d4 directory while /dev/sda6 was unmounted, just to see what happens.
Then I mounted /dev/sda6 again, did ls of /srv, and it showed both dev-disk-by-uuid-6919b6e7-2b51-4384-b2e6-67b8109762d4 and dev-disk-by-uuid-e9fffc3c-2a02-4fdb-a79a-f7c684eb9f7e as normal. cd'd into dev-disk-by-uuid-6919b6e7-2b51-4384-b2e6-67b8109762d4 and did ls, and showing the AppData and ServerFiles folder, along with dev-disk-by-uuid-e9fffc3c-2a02-4fdb-a79a-f7c684eb9f7e (not normal? because that dev-disk folder is /dev/sdb1). cd'd back to /srv and it's still not showing AppData and Server Files... for now.
I then thought about the fact that /dev/sda2 was still showing in File Systems (where my OS is installed) because I had previously installed the sharerootfs plugin because I was having trouble getting /dev/sda6 to show (as explained in my other post linked in my OP here). But when I uninstalled omv via ssh, I had installed sharerootfs along with it there. However, upon reinstallation, though I did not install the sharerootfs plugin again (realized I don't need it), /dev/sda2 was still showing in the File Systems page in the GUI. I wondered if maybe this had anything to do with it, so I installed the sharerootfs plugin again, and then uninstalled it via the GUI, and now /dev/sda2 is no longer showing (as expected).
So I decided to unmount /dev/sda6 again, and THIS TIME, when I went to mount it again, it showed (I didn't need to do the lazy umount command). So I mounted it without issues. The AppData and ServerFiles folders still weren't showing in the /srv folder, however, the dev-disk folder for /dev/sdb2 was still showing within the dev-disk folder for /dev/sda6.
I'm hoping someone can explain what's going on, and if any of this is normal behaviour, and if I have anything to worry about.