Answer:
My brother and I are two different people. Would you let one of us "give" his account to the other? wink
The sole proprietor and the partnership are two different people. If he wants to close the partnership account, he can write himself a check and deposit it to his newly opened sole proprietorship account.
If you allow the conversion of an entity account to a single ownership account you just disenfranchised the other owners. They may not like it.