I cut up a piece of crab apple; the main trunk just before it split into 4
trunks.

One half is very light and porous; I would call it willow if I didn't know
where it came from.
The other half is heavy and solid; pretty much what you would expect from
crab apple.
From the outside they looked to be the same.

Is something like this common? Anyway to determine it before cutting? I am
just lucky I cut it in half on the axis I did.

I have turned one bowl from the light side. Terrible tearout and it would
have absorbed as much LBO as I threw at it, but it turned out nicely. I am
hoping the hard half will be even better.