Yes, the loan can be signed first but the money won't be released until the car has arrived, you have paid the balance and it has been registered in your name.

Some dealers require you to pay when the car is allocated to you and arrived in PDI hence you have no chance to inspect the car first. If possible try to delay payment until the car has arrived in the shop and you can inspect the car. The car will be in PDI at most 3 days.

Of course once you pay the balance you can no longer reject the car.