Exactly 6 months for a transit visa from US to India via UK

Before you close this for being a potentially duplicate question, please understand that I have seen some of the questions and what I'm asking is a bit different.
As I understand, one would need a DATV if one won't be crossing border control in the UK. But the wording on their site is,
You won’t need a visa if you: are traveling from Australia, Canada, New Zealand or the USA and it’s less than 6 months since you last entered that country with a valid entry visa
A relative of mine is traveling in 2 weeks time and will be leaving the US exactly 6 months after arrival. So while its not exactly less than 6 months, its not more either. It's exactly 6 months. Would my relative be required to apply for the DATV? He is a citizen of India.
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Does London need transit visa from US to India?
You should apply for a Direct Airside Transit visa if you arrive in the UK on a flight and leave again without passing through immigration control. Since it has been more than 6 months since i last entered USA, it looks like ill need the transit Visa to travel from USA to India via London, even if i stay airside.Do I need a UK transit visa if I have a US visa?
You're going through UK border controlApply for a Visitor in Transit visa if you'll be going through UK border control but leaving the UK within 48 hours. You'll need to apply for a Standard Visitor visa if: you need to stay longer in the UK. you can prove you need to frequently pass through the UK over a longer ...Do I need transit visa for connecting flight in UK?
You might need a Visitor in Transit visa if you're: changing flights in the UK on your way to another country. going through UK border control, for example to check in your luggage for a connecting flight. leaving the UK within 48 hours.How long is a US transit visa valid for?
How long is a US transit visa valid for? The Transit visa only allows for the layover, it does not permit other activities or longer stay than necessary to proceed with your onward travel. C visas are generally issued on the earlier date of either the departure date on your ticket or up to a maximum period of 29 days.Transit Visa Required For India - Schengen - UK Route
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