since they are just normal people and had no concept of chakra and the techs that come with it, this is how it appears to them.
But once ninjutsu was a common thing and that people are more aware and can perceive more as they are more attuned to the things that are going on, ninjas can see things normal people can't.
Basically, this is the point of view of someone who has not experienced any powerful techs but for someone that has, for example ninjas, they might see her use her byakugan and possibly gentle fist.
Even though it was merely just in the blink of an eye.
