That is strange. Instead of just pushing the 'Migrate' button and moving your account to BIS 2 they would rather go through account deletion?
Here is the difference between these two approaches you should be aware of: if they migrate you, your old user name will be preserved. If they delete your account and create new- you might not be able to reclaim your old user name. Chances are slim but it did happen with the person I know.
So, if you really wish to keep your old user name- call customer support again, tell them look for migrate button. If you are OK with possibly changing user name and blackberry email address- let them delete your account.