Steve, what actually happens is that a battery failure leaves you with a bike stuck in gear. Which can be even more inconvenient than one that won't start in neutral, because of (say) pushing around.
A dead bike is bad enough, one that can't be moved is the pits! This leads to a load of, bad tempered, 'DCT stuck in gear' posts which should really be 'battery problem' ones.
Like everything, it's personal choice. I always put mine into neutral and stopped it using the key (rather than the kill switch or stand switch). Same way I 'shut down' the computer rather than just y