How much do bittering hops contribute to flavor? Does a hop addition at the beginning of a 60m boil result in the destruction of most that hop's flavor compounds?
The 60 minute addition does indeed contribute to flavor. Its not much but its noticeable. Especially the higher alpha acid varieties. I have brewed several single hops beers with a single shot at 60 minutes, and you can definitely pick out some flavor differences between hop varieties. The beers aren't all simply bitter with no flavor when compared side by side.
However, to really get appreciable flavor additions you still should use some mid boil hops. I tend to like 10 minutes for max flavor effect. I don't think you can actually quantify flavor though.
Of course taste and aroma are so closely related mechanically in your nose and mouth its impossible to not have something super dry hopped and thing that its also got a big flavor addition.
I've added a load of hops only at flameout, with a single 60min addition. The nose is amazing but you'd swear there were mid boil hops added too.
Bittering hops contribute little to flavor - most of the flavor compounds have been boiled off - or at least, that's the common wisdom. To maintain flavor, hops should be boiled for round 20-30 mins, or dry hopped.
You could do an experiment - boil the same amount of hops in a quantity of water for different lengths of time - 60 mins, 45 mins, 30 mins, 15 mins and 5 mins to see the affect on flavor and aroma.
Although utilization is lower with water, that's not what's important here, and using water rather than wort will be sure your solute has no appreciable flavor or aroma that might mask that from the hops.