Hehe; the Wein cells are just a trigger as far as I know. Any sharp edge in light received (e.g. a flash triggered nearby, or the square-waves produced by a TV remote's LED) closes a triac and triggers the flash.

I expect Bowens uses a similar approach to the TV remotes with a bitstream AM-modulated onto a 40kHz carrier for ambient-light rejection, if only because those IR transmitter and receiver modules are cheap and ubiquitous. If I had a remote I could discover the protocol but of course I don't...