Just wanted to follow up:
I made a Summit Amarillo Citra IPA, and used Summit as the bittering hop, and also an ounce of the Summits per 5-gal keg as a dryhop, in combination with an ounce of another hop.
The beer before dry-hopping was very clean tasting, with no onion-garlic flavor at all, but of course somewhat lacking in hop aroma, although not bad since I did a 45-minute hop stand following plenty of late addition hops. I always dry hop my pale ales and IPAs.
Anyway, I dry-hopped in a nylon hop sack in the keg for 3 days at 65F and 4 days at 35F, and then squeezed and removed the hop bag.
Following the dry-hopping, the beer had significant savory overtones with a bothersome onion-garlic flavor, although after a few minutes in the glass exposed to air, the onion-garlic would dissipate mostly, making he beer quite enjoyable.
It took the beer approximately 3 1/2 weeks stored at 34F in the kegerator for the onion-garlic to disappear completely, and now it has a wonderful orange flavor that balances well with the other hop flavors, and I have a delicious, juicy IPA.
So the lesson I learned is that with patience, even when used as a dryhop, in moderation, late season, dried-on-the-vine Summit hops turned out surprisingly delicious. And I didn't get any onion-garlic flavor at all from them prior to dry-hopping, when used as a bittering hop.