Without getting into the safety issue of use of electronic devices during takeoff/landing, I'd say the FA was correct. On just about every flight I've been on in the last 10 years the spiel about electronic devices has included "anything with an on/off switch". This would include a flashlight.
I've never heard the "anything with an on/off switch" part of the directive - but then most of my flights are not in the USA. All I've heard is "Switch off all electronic devices." If they really want to enforce the rule, then your quoted addition makes sense, because I sometimes wonder how you define an "electronic device".
If a flashlight switched on could affect the plane, which I highly doubt, what about a heart pacemaker or an intra-cardiac defibrillator? Both of those transmit signals and cannot be switched off.
I've yet to see any reliable study that proves electronic devices affect flight safety and, like many, I think the rule is silly. However, I do usually comply with it. I just wish it made sense to me!