Most brokers- such as coinbase- perform their transactions using off chain methods. All the bitcoin in coinbase is held and owned directly by coinbase, and what

Most brokers- such as coinbase- perform their transactions using off chain methods. All the bitcoin in coinbase is held and owned directly by coinbase, and what users of coinbase actually have is a database table somewhere saying how much of coinbase's coins are marked as being owned by the user. Celsius is similar, but they also offer a loan system on top of it. So the coins you give to celsius are not only no longer owned by you, but they're also not even present in a Celsuis wallet.