The wing strobes do have a double flash - period. It is nowt to do with your brain or your big toe.
As a strobe power pack gets older, it loses it's ability to fire and hence they will either fire once, or fire out of sequence.
Our Whelen strobes on our RV fire 4 times - it is called a Comet Flash and when on the bench you can clearly hear the 4 discharges through the power pack.