That is hard for me to say because I have not necessarily read the same studies as you have.
Let me paraphrase one the witnesses. As he said, for a police officer to be able to require a person to submit to screening, they must at least have reasonable grounds for suspicion. In practice, it is easy for a police officer to come up with those grounds. The threshold is already quite low and, if it is lowered even further, that would open the door to situations that could become abusive, such as searches that are in violation of section 8 of the charter.