well I think many folks don't do scent control when setting camera's up, and that can be whats spooking them more than the flash
plus many camera's make sounds as they take pictures, and again thats not the flash causing there attention
sure some deer might not like the flash, I think its more of the shadow it makes than the flash
but over the yrs, I never have any bucks avoid any place I set one due to the flash
and I get tons of critters besides deer too on flash . I still prefer a flash for pic quality over any possible scaring animals!