I think that for an FI at a good height over a large useable runway, you'd struggle to make a criminal charge stick. However, he might still be being silly.
I had an FI turn the switches off on me many years ago to make a point. We were overhead a 4x1 mile area of landable beach, and it was certainly not endangering anything, but did teach me something about handling and performance engine off. Landed, re-started, flew home.
G