GMAT Strategy

Today I gave a MGMAT test. When I was on the last question of the quant section, time was running out. I had selected the choice but couldn't confirm it because the time ran out instantly. The section was submitted but when I reviewed the test, that last question came "NA" (Not Attempted). I thought that if we don't confirm but have selected the choice, it will be automatically confirmed as the time runs out for the section but this wasn't so.

Can anyone please tell me that this is the case for MGMAT tests only or it will happen for real GMAT as well? Do we have to confirm the last question in the section before time runs out or it will be automatically confirmed ?