> All education in India happens in English

That is incorrect. In urban areas in India, schools teach in English but in rural areas it's in Hindi. In urban areas, only if it's a big city, then peer to peer communication is in English. However, in other cities, the only interaction in English is with a teacher; other times is in the native tongue.

And even if the students in big cities are learning mainly in English, the teachers are usually not native English speakers, which means that the grammer/pronounciation suffers. which is what you see with Indian engineers that have migrated to other countries.

https://www.quora.com/What-language-is-used-in-schools-in-In...

You are accurate of course - but for the entire sample set that would even be in the running for a computer science test would be entirely native to english for most of their lives in India.