The sound for move on observed or examined game is
played even on non-move events which send board update
like [bw]name, clock changes, etc. I don't know if it
is feature but I found it confusing as I observed GM
games while doing some other work and switched to
eboard when the move sound was played only to find that
none of the positions changed.
We have discused this on-line. I'm adding it here just
to remind you.