Several years ago, we were doing a remote flight test at an operator (the configuration we wanted to make a change to was no longer in production so we had to use a customer's 767 to test it).
Part of the required flight test profile was to do an in-flight shutdown/windmill relight. We do this all the time in Boeing flight test and don't really think much about it, but the operator's line pilots that were riding along were aghast - intentionally shutdown one engine on a twin in-flight? As soon as we shut down the test engine, they both pulled out their phones and started filming EICAS...