I thought WD-40 started as fish oil or peanut oil, but now it's a Petroleum based oil, which is just plain bad for wood. You wouldn't rub Vaseline on there, would you?
I'm sure if someone explained this to the mechanic, it wouldn't matter, much like it hasn't mattered for some naysayers in this thread, LOL!
BTW the WD in WD-40 = Water Displacement
since water & oil won't mix
which is just supporting my ongoing assertion that oil doesn't moisturize