You need to clearly explain what your dataset layout looks like, what is being shared, and what share you are accessing from Windows.
All of this matters.
Datasets, even child datasets, might be confused for folders. This can cause confusion and weird behavior when accessing a “folder’s” previous versions in Windows Explorer.
Are you accessing the share of the root path /mnt/MAIN/tank via Windows Explorer? If so, then the “folders” tank-apps and tank-apps/app1 are technically the root path for child datasets with their own snapshots.
What if you create an SMB share that points to /mnt/MAIN/tank/tank-apps/app1 and then access that with Windows Explorer?
You should also understand that if a file is not modified then there is no “previous version” to restore.
If you want to restore a deleted file, you might as well navigate to the hidden snapshot directory, find the file, and then copy it over to its respective folder in the current writable share.