No, as best as I can tell, this organization is not properly authorized to issue IDPs.
IDPs are regulated by treaty, which states:
Contracting Parties shall recognize … Any international permit conforming to the provisions of Annex 7 to this Convention;
as valid for driving in their territories a vehicle coming within the categories covered by the permit, provided that the permit is still valid and that it was issued by another Contracting Party or subdivision thereof or by an association duly empowered thereto by such other Contracting Party.
This means that only governments or organizations formally authorized by governments may issue valid IDPs.
The AIT/FIA (an international association of national automobile clubs like AAA) maintains a directory of organizations that have been officially authorized by their respective governments to issue IDPs.
internationaldriversassociation.com says they are based in Singapore, and the AIT/FIA directory says the only authorized Singaporean IDP issuer is AA Singapore.
So yes, this website (and many others like it) will take your money and send you a booklet that looks a lot like a 1949 Geneva Convention on Road Traffic IDP, but technically speaking, is not. It is no more valid than something you could make at home with your own printer.
Of course, this unofficial document looks "correct" and may pass a cursory glance by the disinterested rental car staffer or even a local cop, but if you ever ended up in court, you would almost certainly be found to be breaking the law — definitely that you don't have a valid IDP, and depending on how aggressive they want to be about it, you may even find yourself being prosecuted for using fraudulent documentation.
The directory says there are 4 organizations in India authorized to issue IDPs:
I'd imagine at least one of these organizations will be able to issue a proper IDP to you.