"Unconditionally stable" is a term recognized
in maritime parlance as hyperbole.

Only by those who fail to understand the designs involved.

such as design engineers?

unconditionally stable means stable without an condition contradicting it.

Catamarans are usually UNstable in conditions beyond about 30* of heel. In
fact, catamarans are most stable ONLY at zero degrees of heel. Each degree of
heel past zero takes less and less force to push the boat to the next degree of
heel. In addition, as the windward pontoon clears the water the wind force
heeling the boat *increases* due to the end plate effect of the leeward
pontoon.

Both are in dramatic difference to monohulls, which in cruising designs are
more resistent to heel as the boat tilts (up to about 60* generally of heel)
and in which the sail area exposed to the wind decreases.

Catamarans can be capsized by strong winds alone. Monos virtually always
require breaking waves to capsize.

There are, of course, some deliberate design choices such as
a relatively short mast and sails which are calibrated to offload
dangerously high forces before the craft is in danger.