The question I have is...how would someone have used ANY GFI unless thay had already used all of their normal movement?
That is just it. The only time you are not forced to make the 2nd block is if you are out of both normal movement and GFI's.
If you didn't put the 'out of normal movement' part in there, you'd rules lawyers trying to say that "I have 1 MA left, so I CAN'T go for it again, therefore I don't have to throw the 2nd block."
And if you left the 'Can not go for it again' out, you'd get other rules lawyers saying that since I have no more normal movement, I'm not forced to make the GFI to throw the 2nd block (and this would almost be a reasonable thing, since this is how it works in LRB4)
Because of the interaction with sprint (and possibly a card or two), you can't just say 'have gone for it 2 times already' since there can be situations where you have gone for it 2 times already but still are able to GFI again.
So, you have to restrict the condition on not throwing the 2nd block so that to satisfy the exception, you must be out of Normal Movement and are out of GFI attempts (normally by having gone for it 2 times already).