Since you mentioned that we no need to put same address in dashboard then we can send BTC even without opening an account in
https://nvo.io/? site right?
You could, but it is absolutely not recommended.
Anyway, I have put in the same BTC address in my dashboard and sent BTC from the same address.
Besides better support, there are cases where users may send from several addresses at once (in the same transaction). One way to determine which address they will receive their tokens on is by querying the address that they've put into the dashboard.