It is not necessary to attempt Indian & Global environment section of MAT exam as you said correctly that the composite score on which you will get the actual percentile. So you can save the time of attempting those 2 sections and increase your marks and accuracy in other 4 sections which are actually evaluated.

But you need to remember one thing that for these 2 sections you are allotted a separate percentile and generally during interviews you are asked how much percentile you have received in these 2 sections. If you won't attempt any question then with zero percentile it can create a negative impression and can be a downfall for you.

So what I strongly recommend is neither to leave those 2 sections completely nor to waste your time in attempting the whole section. So attempt few of the very easy questions which you can get correct in short time. This way you will be able to score a good percentile in those 2 sections and also save time for improving your score in other 4 sections.

All the best!!