The lists under "Reducing Friction" aren't comparable.
In the first list, point 1 and 2 should both be in the second list as well. Point 3 and 4 are the same thing.
Also, often the link in the email would open a page that would automatically do the action for you.
Correct me if I'm wrong but the only real difference seems to be that the button doesn't have to open a new page to perform the action.