It would be the equivalent of taking a test without studying. Training adaptations to speed (or anything else for that matter) are quite specific. If you never run at maximal or circa-maximal speed until you go and race and your talent allows you to run super fast without the corresponding adaptations necessary to do so safely then you have a problem on your hands.
Why is he not doing maximal speed training this far in-season if it would make him faster?
What I’m getting from your reply is that neurally he isn’t prepared to handle those high speeds because if his body is prepared through the weight training, why is it breaking down because of sprinting? I’d expect him to have weight training related injuries.