Monster speed to global opens up flexibility in having multiple monsters or even other types of sprites read that info... for example if I have a turret or something else that needs to know the speed of a target to adjust it's bullet speed, that is a useful piece of info to have in a global variable.
You will find that many tutorials have some additions to their event sheets as the tutorial usually focuses on some specific pieces, and the event sheet may have been used for multiple tutorials, or even come from a game prototype they were working on when they had the idea to make it a tutorial.
Also, some of the additional items in some of the event sheets lead you to better understanding of different concepts, etc...
As long as everything in the tutorial is in the event sheet and nothing is left out, then there shouldn't be an issue with having more items in the event sheet to look at as long as they don't take anything away from the tutorial.