How does it outperform solid wood? Most solid hardwoods can handle loads
in excess of PLY?

Not cross grain

Yes ply is acceptable... absolutely.. but I don't know other than price
how it outperforms solid hardwood.


Stability

I like the spline and reglue idea,

Odd, I think it is terrible idea. I put a lot of work into matching to
avoid seeing glue lines, and he is creating them for no purpose. Well, each
to his own.