It's an interesting point.
They are trying to not change things, on the surface, even when they do change reality. Even saving Sousa was done in such a way to mitigate the impact. Although with no body left, did shield just ignore that and proceed with a funeral? I don't remember if he had any family although he wasn't married. The lost body would have an impact, I'd think. Maybe not?
Leaving Enoch in the past and Patton seeing the ship would likely have some impact.
I try not to think too much of the rules in time travel movies or shows.