What if you press Ctrl+X twice on separate regions and then press Escape (once)? Does it restore the state after the first Ctrl+X? So Ctrl+X pushes on a to-be-cut stack and Escape pops? Probably not.
Anyway, this looks like it means that the inability to undo the change in clipboard state is replaced by the inability to return to an earlier to-be-cut state. Or maybe the editor includes a Vim-like time-travel history that includes the to-be-cut state?
Regarding the clipboard state, given that the clipboard is an OS-level object, for me it makes sense that an application-level or document-level undo doesn’t undo changes in the OS object. Similarly, undo after Save doesn’t undo the change in the file system state. Of course, it’s fine to provide alternative editing operations in addition.