This reminds me of the times when we would pug in WoW, and a player would be wearing tank gear for dps, dps gear for healing, and similar mashups. We never kicked them, as they were quick to explain they were building an offspec set of gear. Sure, they weren't optimal, but we didn't mind. They were good enough at their job, and we were quite willing to help them acquire the gear they needed.
It's all about honesty and professionalism. The math is there to help fix and prevent problems, not cause grief.