And it would be OK for a jumpseater to not interrupt the Captain during takeoff. Especially, when it's a non safety of flight issue.

"I recall riding jumpseat in a G159, I knew the aircraft quite well. The crew had missed a preflight checklist item and as the pilot was advancing the throttles for take off I asked if the windshield heat was supposed to be on."

Could this have waited till a less critical phase of flight?