I understand what you describe above. The lock Texture should lock it for all objects that share the same single texture, as the Single Material Mode suggest to share a texture. However, the UV(W) tag is not exclusively bound to this Single Material Mode agreement. But think of other shared textures from other channels. It can be quite a complex investigation of what is where and used by… etc.
So, there is perhaps the reason to keep the Lock-Texture mode per single object only and ignore the shared texture as the connecting element.
Yes, like the Lock on the Attribute Manager, it is for the Object. Especially when you select several objects at once, and then lock it. It keeps the number of objects. Which would be expected to be the same for the BP-UV Edit options, while locking the Texture.
The way to work with the given options is: If you have a single Texture that you would like to lock, do it. It will stick with the current UV Tag (and with it stick to the object). It will not switch anymore. Keep the lock, but go into the UV editor view, in the menu>UV Mesh>UV Tag> (chose from the list)
Of course, I might miss something (I always assume that hence why I like to dig deeper, but am I always digging deep enough?)
One way would be to voice your needs in a Suggestion
Or just get in touch with the support.
But of course, if there is anything else that I have answered or what wasn’t discussed so far, please let me know, I’m happy to look into it.