The way how you raised GMAT issue tells the state of your Maths ( and analytical) skills in my book.
I learned this word "GMAT" not long ago here in PDF. I had never heard about it before.
Average GMAT Maths score doesn't count, because it has self-selection bias inbedded in the sampling:
Not every joe in India takes GMAT Maths test, only the best, at least significantly above average ones, take it.
This is because the ones who take the test have (rightly to be) self-confidence trying to enroll into a US uni - this tells their average statue among their indigenous population there in India.
Hence that some "good apples" are good after all at GMAT Maths doesn't reflect their average whole basket of "apples" at home.
I almost can bet that India's average GMAT score is probabaly even higher than that of Netherlands and Belgium, or Germany ( these countries are centered around Top 10 in PISA Maths world ranking and definitely WAY above that of India).
Why this contradiction then?
It's because here in Holland( Belgium, Germany) , the best studs usually don't go to the US for uni, but staty here at home for home-grown technical/economic/medical schools , for example, I had never heard of GMAT before. Those who took GMAT Maths and went to US to study are usually average studs here, centainly not top tier in most cases. This contracts with India where GMAT-takers are usually among the best of the crop.
So GMAT scores are biased and can not be counted as "stats" to showcase that Indians are good at Maths.
On the contary, PISA Maths scores do count, as PISA has no self-selection problem as random sampling decides that
every school kids concerned are tested and counted.
The exactly same reason applies to examples/stats of how Indians in America or in the UK blah blah....
ADDITION:
In fact, despite of the fact that there're many Indians who are good at Maths ( due to its large population base where even 0.00001% of 1.2 billion are a lot! ) , there is
sufficient theoritical basis to suggest that average Indians are
not only NOT good at maths,
but also Bad at Maths -
significantly worse ( about 2 standard deviations below)
than the averages of Europeans and East Asians.