Anyone who intends to buy a house gets such a slip if they want, stating that they are liquid in the event of a purchase. In your case, it would be the house bank where the equity is held.
Am I or are you missing something? Why would you have to pay more interest on the loan? Whether you start repaying the loan now or in 2 years makes no difference, right? Or do you want/can only start repaying when the apartment is finished?
The tip to prioritize the loan first is not wrong. It's best to contact an intermediary and clarify the disbursement. By the way, I see it positively when a loan is disbursed promptly. This way, you also start repaying immediately upon full disbursement.