Enabling and disabling themes from the network admin has no effect on the sites. All the sites continue to display their own themes. Even network-disabling all the themes has no effect. Installing new themes has no effect on the sites. They don’t recognize a new theme has been added. The only effect the network admin can acheive is to delete a theme. Then all the sites stop working. How do I fix this?
Multisite theme control not working
I believe you’re not seeing how themes work on MS setup. Enabling a theme via the MS settings makes it “network enabled”. This means it is now “allowed” to be used on all the network sites. If you don’t enabled it, network sites will not even have access to it.
Network Enabled does not mean it will use that theme on all network sites as you are thinking, it simply allows it.