Right. What I meant is with the rare tag you can't horde multiple to pop all in a row, but you could send multiple to yourself, and port back and fourth in between kills with minimal downtime. As you said, they decided that they'd just block dboxing as well to prevent too much spamming in a short time, outside of additional characters being present to pop. If dboxes did pay notice to rare tagged items, I'd imagine they'd be sendable.
I has nothing to do with the rare tag and everything to do with being a "bazaar" item. Crap you can only trade or bazaar not send to other players or sell on the AH. Sky pops, ancient currency, forgotten stuff, ABC's etc. Currency and ABC's aren't rare but you still can't dbox them to the same account. Dice and residue didn't use to be sell-able in bazaars but could be sent to same accounts, which is probably the only reason you still can send them. I wish they'd change this policy since it's a pain to bug people to trade bazaar items you get randomly from flotsam etc.