bittrex is legally obligated to provide the distribution for the bytes held on its platform regardless of the option of withdrawal. This is like a stock broker taking the dividend of your stock from you.
No private key nor bought over platform, no rights of possesion. Quite easy to understand if they dont tell you different.
We need more exchanges for BB not less, i was thinking. Therefor you have tradeoffs. You are making the 10% over trading on bittrex or by holding them in a wallet. Its not different with pos currencies. We dont need to fight wind mills or the feeding hand.