The specific answer to your question: can't say, really depends on university admission statistics. However, there is one thing that these schools certainly won't do. They won't be as successful as people think they will at inducting kids who go to them into those global elite networks. The logic is obvious, so let's address it point by point - here's the stuff all those people quoted in the article won't tell you, from an Indian who actually lives in the UK.

1. Key point: they are the outposts, "offshoots", not the real thing. They aren't Harrow. Or Charterhouse. No Salopian, Harovian or Carthusians are going to treat these graduates as one of their own. This is because these schools would be viewed by them as fundamentally different. Their "catering to the local environment", operating on a different calendar, adapting of the curriculum... all that makes these guys second-class. For god's sake! George Malory went to Charterhouse - the guy who might have been the first one to climb Everest - we don't know. Obviously, great flex for a Carthusian. You think any Carthusian with even the smallest amount of common sense will allow some Indian interloper to claim that legacy, too? Of course he won't - especially if he is an Indian Carthusian (ie, one who went to the original Charterhouse in the UK)!

2. Culturally, these guys might be brought up to be similar, but they're certainly not the same. Working on Indian dramas in your acting class? Sorry. Unless you're doing the British cannon, you're different in their eyes - doesn't matter if you went to one of these schools, one of the local international schools, or an Indian board school.

3. That ▮▮▮ woman in the article says they "don't care about exams"? Damn it, the British are a society who are very unforgiving of academic failure! If this is true, then these schools are fundamentally un-British in their way of educating people. At Eton, for example, they used to (not sure if they do anymore) have a custom where if you performed badly in a test, the teacher would return it with the paper ripped in a corner to you. Eton publishes statistics about its GCSE (10th grade board exam) results on its website. The universities in Britain don't have this culture of allowing students to make up for failing an exam without severe mitigating circumstances by repeating it, taking the repeat seriously and then performing well in the repeat. You get only two attempts at an exam or assessment in any module/course you take - the first, and if you fail that, a "resit". And the resit is really not much of an attempt anyway, because the universities restrict how much you can achieve in that attempt to and give you the minimum pass mark only, not the full grade. That's unless you have evidenced mitigating circumstances (like death in the family), in which case the "resit" is treated as a first attempt, and there are no caps imposed. I personally saw this happen to a friend of mine while studying at university in Britain and went through the uni's academic regulations (and those of comparable unis), so am not bullshitting. Do you really think a culture like that will be suitable for students who went to a school that "doesn't care about exams"??

4. The comforts described are also fundamentally un-British. Read up on Nehru's writings about his school experiences. Cold showers, for example. One of the bonding factors for British school and university alumni is to talk over those kinds of things: being forced to take a cold shower (because the water heating system was out of order) on a winter's day, for example.

Therefore, from an Indian in Britain (and educated there after school): Parents, either send your kids to the original versions of those boarding schools (12 hour flights away) or send them to a typical international school in India, if you are sure you want them to migrate abroad. Or even just send them to local schools and save loads more money at that stage. If the kids are clever enough and you (and they) play your cards right, as that person said about the hypothetical ISC and IB candidates, they'll manage to get through the British unis nevertheless, and might even secure a job afterwards - there are plentyful examples of such in the legal sector in the UK (Indians who were schooled in the local schooling system, went to unis in the west and are working at high-paying law firms). Because I'd certainly not send any kid of mine to these places.

Context: https://theprint.in/ground-reports/new-british-boarding-schools-latest-accessory-indias-rich/2753964/

Sure. IITD, IIMA, NLSIU, Campion will always be at the top. But these are just the top 1%. What about the 99% others? Gradually losing out to expensive, international-style private schools and colleges?