They just showed Jedi that were intensely engaged in combat or at least actively focused on their known foes, so that explains it a bit. Maybe the unengaged Jedi in the Temple would have been more able to detect the intent of the force marching their way.
Also could be due to a certain degree of blindness towards the troopers due to their clone nature. I think that the nature of their cloning and mental programming might affect their brains in such a way to make them more automatons than emotional actors of their own free will, thus masking what in most people could be felt as personal desire or consideration.