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.