I don't know anything about ShakePay, but MOST exchanges pool the bitcoin funds together.

When you ask the exchange to send out some bitcoins on your behalf, they generally will be sent from a pool of bitcoins that the exchange has control over, and won't necessarily be the same bitcoins that they received when you deposited them.

Banks work the same way with cash.  When you deposit cash into a bank, that cash gets mixed together with all the other cash that the bank is holding.  Then when you withdraw your cash, you don't typically get the EXACT SAME bills that you deposited.

Why does the ForEx broker care if the address is the same?  He should just send the funds wherever you ask him to.