Binds on battle.net account, means, it can be sent around in a battle.net account via ingame mail excactly how them mail works.
I can send heirlooms to my warlock on different world of warcraft account, because they are on the same battle.net account and realm.There. Binds on Battle.net account working as intended.
I bold part why sending looms dont work perfectly
battle net account can have 50 chars on different realms, and if sending looms works perfectly I can send them to any of my 50 chars no meter on what realm they are ....
battle net account isnt 8 chars you can max have on one realm
''bind to battle net account'' = to any of my 50 chars not only 8 where I buy loom
Nowhere is it mentioned, you could.
But it mentioned you can send them to another character on another account on the same Bnet account.