Hi,
It seems but in fact no.
When you select a shipping/payment method ; it will affect the order by changing is price for example.
And also selecting a shipping method could allow you to select some payment method which wouldn't be available before.
But when the cart price changed, there is an obligation to display the final total to the customer before processing the payment.
That's why using an option to auto-select or to automatically submit when selecting ; allow to always display the final total and process the payment when the user click on "finish".
This kind of problem will be fix in HikaShop 3.0 where we planned to make a refactoring of the checkout (using ajax and dynamic refresh).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.