Most authorities require the Flight Data Recorder to be on prior to engine start. To the best of my knowledge, all Boeings and most Bombardier aircraft do this by slaving the FDR ON to both of the Strobe lights
I'm sorry but your knowledge is incorrect. I don't know about Bombardier aircraft but on boeings the FDR is turned on by either air/ground sensing, engines starting or running, or for testing purposes. Strobe light (white lights)or indeed Anti-collision (red lights) switching has no input whatsoever into FDR.