Thanks for another great xBmt, Marshall! When I do batches of single-hop trials, I definitely notice a difference in the quality of bitterness between the different hops. It would be interesting to go back to some of my tasting notes and see if the CoH levels line up with my experience.
I wonder if this has any bearing on why beers with no bittering addition (i.e., all IBU's from the whirlpool) seem to have a smoother bitterness than those with a traditional 60-minute addition. It could be just hop choice coming into play, but maybe less iso-CoH is produced by that technique. Every time I see one of these experiments it makes me wish I had a GC/MS in my garage to help answer the myriad of other questions it seems to lead to.
Given the narrow margin of significance on this one, I'd say this would be a good candidate for an IGOR followup, to see if a bigger sample size will result in a clearer conclusion.