I think we agree. Sure, if he's sandbagging, distracted, and not meeting expectations, that's unacceptable. But the (maybe theoretical) superhuman who can successfully juggle multiple full-time jobs and perform as any other full time worker would be expected--I don't get why it's taboo. Maybe it's something magical in the "employee" word, since independent contractors can, and many times do, have multiple simultaneous clients, and it's not a problem.