I agree with that. Quickness and explosion are different than speed. Chism III is very quick, less quick than Edelman but quicker than Welker. Usually people look at broad jump, vertical, 3-cone, and short shuttle to gauge explosion. The 10, 20, and 40 yard dash indicate speed.
Chism has the build and scores to match a very quick slot reciever, but his 40 yard run was surprisingly slow, like all-time low for his body type. So Chism is at the extremes, really quick and really slow. We will see if player can depend solely on quickness in the NFL while being so slow. Edelman, for example, was much quicker and much faster than Chism III, so that comparison is not valid. Comparisons to Welker are valid, so maybe Chism III will be very productive. He is a strong guy so I think he will hold up OK. It is a very interesting skill type.