All I can say is that the lawyers would have a field day if it went to court and all you were able to say is that "it looked right at 100 kts."
Why do so many people have a problem grasping the concept of this extra check?
The point of this check is to insert another safety mechanism on the takeoff roll, in order to prevent an aircraft becoming a very fast mode of ground transport.
In your example, the crew had chosen to commence the takeoff roll, meaning ipso facto that they were happy with their configuration and calculations to do so.
Without any intermediate check, they would have continued the takeoff roll anyway! By this (ficticious for the example) crew saying "...it looked right at 100 kts..." does not have a bearing on the outcome -
they were going anyway! Thererefore legally it has no meaning.
The
only way the 100 kt check can change the outcome of a departure is for the crew to abort the takeoff, turn around and have another go; after re-assessing their configuration and calculations. Hardly unsafe.