Is it just me, or does that seem pretty stupid? That's not a "synergy", that's what the spell does, make wood hard (heh). It's certainly not being used "in conjunction" with anything. I think this was simply an oversight, a mistake that they aren't living up to.
It's no really that important, I guess, but is it just me?
"If you fudge dice rolls, your system is failing you!" -Sons of Kryos
"I genuinely think that some people measure their free will by reading how unhappy their GM is." - TonyLB
[dice type=fudge]3dF[/dice]