I don't think he would be expected to learn the entire playbook but have a grasp of the scheme, understand first reads, what his OLine calls are (even if he isn't the one calling them). I don't know how common this is but I don't see why it isn't reasonable if a team is unsure if a guy fits with them or is worthy of being a top 5 pick. He wouldn't be doing this for all 32 teams, just the ones that will potentially draft him and he has multiple meetings with. Maybe that is 3 or 4 at most.