It is entirely possible that even if Windows 10 was perfect software according to the "it gives you the correct output for every input in the input domain" definition, it would still not open the start menu every time you clicked on the icon.
Of course we can redefine bugs as features, but to present that as an argument is a “red herring”: I can assure you, the Windows 10 start menu is not i tended to fail or delay opening instantly upon click or system button press.
