I have looked at your video but it doesn't tell me anything about the Arduino system.
I have been trying to match the information you have given me and the information I got from a brief read of the PDF for the scale interface.
I thought you said that 10 steps of the motor cause 1mm movement of the spring (or whatever). And that one reading of the scale every 0.1 seconds would be adequate. I put those together and came to the conclusion (perhaps wrong) that you need 10 steps of the motor between every scale reading and that would correspond with one step of the motor every 1/100th of a second. (And, yes, I know this is not watertight logic, but it explains my thinking).
Can you confirm if I have understood you properly, and if not please correct me.
Then you ask if the stepper motor will stop every 1/100th of a second and the answer is probably YES. That's how stepper motors work. I say "probably" because the momentum of the motor may carry it forward while the load will try to stop it.
Hope this helps.
if not, please try to explain what you don't understand.
...R