Non admin users do not see cross scope update warning messages like;
This record is in the Global application, but {{application}} is the current application. To edit this record click here.

Only a user with the admin role will get this type of message.

As a result updates may not end up an the expected Update set.

A scoped admin user (role like x_myscope.admin), who is for example catalog_editor could be in the applications scope context.

From there open a catalog item from the global scope, but not get the message.

There is no workaround other than granting the user the global admin role.

Users with low level roles do not have the same concept of scoping (and can not choose a scope) so data is not separated the same way.