Something changed in a relatively recent version of macOS that prevents KM's simulated keystrokes from being able to trigger the default Mission Control shortcuts for moving between spaces:
Fortunately, the workaround Peter describes in that post still works as of Big Sur 11.6. I use it myself with similar macros that trigger new Mission Control shortcuts that would be pretty difficult to type by accident:
Mission Control Macros.kmmacros (2.9 KB)