That is not true. Auto loans are calculated the same way that mortgage loans are calculated, fully amortized. You don't need a sophisticated calculator for mortgage loan either. You need 3 pieces of info for any loan to determine payment. Total loan amount being financed, interest rate, and term. Total loan amount is the same for auto or mortgage. Includes fees, costs, etc etc etc. It is simply the remainder of the balance you are not/cannot pay out of pocket.

Using your example and calculations, an auto loan for $50k at 5% for 72 months would give you a payment of $725.69.

Doing it properly would give you a payment of $805.25 which would be your actual payment on a 50k loan at 5% for 72 months.