Mythbusters test an old samurai saying

I recall some tests that were done that people use to argue for 'defense' being stronger than offense along these lines.

I think the context is wrong...I don't remember the exact tests, but the extrapolation made was that 'waiting' for an attack to actually happen is quicker - i.e. that reaction is faster than action. There might be some technical way to try to "prove" this, but i'd argue that any such proof flies so much in the face of common sense (in terms of martial arts/combatives stuff at least) that it is ridiculous to even entertain it, obviously if it is on, it's just dumb to wait for something to 'react' to..whatever the technical proofs might be.

How many altercations have we seen where the one who "waits" wins?

if there is any truth to be had here, is it possible it has do with the specifics of timing  in dueling, and not with some larger principle of combat? Timing is very different thing between two people who know the other is going to do something and are in 'wait' mode than in broader situations of violence, even when they aren't martial artists.

Personally I see the saying as more philosophical than anything else. Sure it's fun to watch Adam and Jamie beat each other sensless with a couple of shinais, but other than that I don't really undestand why they tested it as it's not really a myth...

And I do believe that they would have much different results if they were allowed to move around, for example dodging the strike to then hit pack, rather than just standing there and waiting for the hit to come.

I would really like them to revisit this one, and do some changes. And yes, training reflexes etc as you talked about Tau, would really have a great difference in results too!