William R. Watt wrote:

I'm sure
if wood only needed to be heated to bend then for centuries boatbuilders
would have been using dry ovens instead of more complicated steam boxes
for bending.

The advantage of steam is that it produces the proper degree of heat
repeatedly and reliably. It's by far the simplest way to do so, since no
thermostats or circulation fans are required. The heat retention of the
water vapor helps assure that the heat is evenly distributed in the box
and it transfers heat 25x faster to the wood than air does. You
certainly could use dry ovens, but on thick stock, you'd end up with a
very dry outside layer by the time the inside heated up enough to bend.

And natives would have left wood in the sun to warm up prior
to bending rather than soaking canoe ribs and planks without heat to make
them easier to bend.

No, because sunlight wouldn't produce nearly enough heat. You're making
some pretty illogical assumptions here.

Anybody who wants to try a comparsion can heat wood
in an oven or microwave dry or wet and test the difference. What we don't
have in this, and many discussions, is any experimental data.

Agreed. The closest I've come is to take pieces from the same plank,
soak some and not others, then bend them. I found no difference in
bending ability, but the tests were hardly scientific.