What is the harm in having players come up and try out at the ML level? The 40 has chaff that can be cut for him. No offense to the kids out there playing well but he's not going to hurt the team's playoff chances.
One of the benefits, historically, to being bad is the chance to bring these guys up and see what they can do.
The data you can get from watching him in the majors has to be superior to what you can get playing scrimmages against the same competition for months.