Hi. Yes, and no. Ultimately
MGMAT is correct in saying that the score you end up with is the score you get.
There are a few other small components that would make that not true but that are rarely coming into play such as failing to answer questions/mark answers/guess.
P.S. The number of questions answered correctly does not correlate to a score on the GMAT so while it does impact your score, there is no correlation since the order of mistakes matters - e.g. if you miss 10 in a row it will be a different score than missing every other one.
The bottom line for you as a test-taker is to focus on answering as many questions as you can correctly and answering as many difficult questions correctly as you can. To get to the difficult ones, you have to answer all the medium ones, and to answer those, you have to answer the easy ones. The key to success is to balance your time and be realistic with yourself. Sure you can answer the first 10 questions at a huge cost of 3 mins per question but is it worth spending half the time on 1/3 of the questions? (the answer is no). it would be a better situation if you are 20 mins in on question 10. Giving up and knowing when to let go is very hard and most people don't plan on it.
BB