I'm no expert but I think the point is that if you lose power, a relay-based system will fall into a known state.
Pesky digital components won't necessarily do the same, being governed less by mechanical physics. That's probably a gross over-simplification.

/used to do a bit of 40XX and 74LS electronics as a kid ...
(BrianHequator was stretching owls, on, or around, Mon 5 Sep 2011, 13:05, 1 reply, 14 years ago)

The known state presumably being one of the switches hasn't (or has) switched
and it's Bartleby's job to figure out which one.
( Kroney, Mon 5 Sep 2011, 13:06, Reply)

I guess so.
That and the fact that a relay-based system has proper bits of wire as conduction paths, so even if the logic power fails (i.e., the relays won't switch) the established circuits are still good, in contrast to semiconductor-based circuitry.
(BrianHequator was stretching owls, on, or around, Mon 5 Sep 2011, 13:08, Reply)

All this is true.

( Bartleby A dead man on vacation, Mon 5 Sep 2011, 13:13, Reply)