On a recent wreck dive trip, the profiles called for a mandatory two-minute
stop at 10m/30' and three minutes at 5m/15', following no-deco dives to a
maximum of 30m/100'.

I don't recall anything about safety stops at 10m/30' during training, nor
reading anything about them on the lists.  I didn't have a problem with it;
I enjoy a bit of hangtime just to look around midwater, optimize weighting,
mentally review the dive, etc.  In fact, I usually go for five-minute stops
at the normal depth.

Is there any proven value to the deeper stop?  I know that they're
recommended for deep decompression dives, by Richard Pyle et al, but these
were all no-deco dives.  Or was this just a means of slowing divers down for
the transition to the 5m/15' stop?  Or possibly a legal requirement?  It was
in Queensland, where there seems to be quite a bit more diving regulation
than my usual haunts.

Also, is there any proven benefit to extending the normal stop to five
minutes?

Regards,
Steven