First of all, Anderson is widely recognized as being a higher value than Spencer. Taking Anderson at 15 would generate alot more applause than Spencer at 15. That being said, the Steelers have drafted one of the players in the first two rounds they have interviewed nearly every year. Woodley, Carriker and players of that nature are coming in for an interview. Guess, who's not: Spencer.
That could change over the next couple weeks, but I doubt it. Every expert and scout agrees that Spencer is a 4-3 DE and is not fluid enough in the hips, the same argument you are making against Woodley.
I highly doubt Spencer will be available in the second round nor Woodley available in the second round. Too many teams need a DE and your going to tell me Tamba Hali goes in the first round last year and Woodley does not?