I've never heard of this either, but I wonder if it has something to do with pesticides or other chemicals, as these things are not always well regulated in China.
Also, it's possible that you may have a slight allergic reaction to something that is destroyed in fully oxidized (black) teas. I don't know enough about tea chemistry to suggest a possible culprit, but I wouldn't dismiss the idea either.
If I were you, I'd order samples of a couple oolongs and greens from Adagio, and see if you have the same reaction. If you still have this blockage with the Adagio samples, then you can be quite certain it's not related to chemical contamination. If you don't have the reaction with Adagio teas, it could still be anything, but then I guess it doesn't really matter too much if the problem has been solved, eh?
Anyway, I think it's great that you're moving on to greens and oolongs. If you do order any samples from Adagio, I'd try the "wuyi ensemble." It has a similar character, in some ways, to black teas, so it might be a good first step into the wide world of oolongs.