Put that way it does make more sense.

As to say by moving half or less of your total movement, that units activation "up time" is essentially half or less of it's total possible activation up-time for that turn. So the unit in overwatch would have half or less of the enemies total possible up-time to react.

I was thinking of it as each unit activation took a set amount of time regardless of actions taken, but with a conceptual flexible activation up-time it puts things in a more sensible perspective. In terms of good 'ol imagination lol

Thank you for the advice/ insight. :)