When I used the word “guest” in my post(s) above I was implying creating a new account that only “guests” would use, not that you’d actually named the account “guest”. Sorry for not making that clear.
The default Public Share not being configurable to Private is a long standing complaint to which WD has chosen to ignore. The unofficial recommendation is to put any files you don’t want others, like “guests”, to see or have access to in a user created Share that is set to Private. The workaround is to create several “guest” accounts. One for your “coworkers” and another for “house guests”, and others as needed.
There are unofficial ways to try and configure the Public Share as Private or to disable it all together. But those methods are primarily geared towards the older v4.x firmware My Clouds. Here are two threads that discuss those methods:
https://community.wd.com/t/can-i-delete-or-rename-public-folder/91213/19
https://community.wd.com/t/removing-public-share-wd-mycloud/137086
Various requests in the Cloud Ideas subforum to hide or set private the Public Share, here are two:
https://community.wd.com/t/manage-public-share-user-access-at-least-a-read-only-option/97231
https://community.wd.com/t/delete-public-share-folder-or-restrict-access/97081
