Regardless he's gone 6 days without water with no ill effects at that age, I doubt he's the 'real deal' - but thats pretty impressive when you consider generally speaking 10 days is meant to be the survival limit without water and your faculties (both mental and physical) are meant to decay as the time without water extends.
How Long Can You Survive Without Water?
As such I'd expect its entirely possible he has a gene or similar which allows him to operate with less water intake than normal people .... so their studying him seems quite sensible.
(personally speaking I doubt I'd be able to last more than 48 hours before I started begging for a drink, I wake up dehydrated and needing a drink most mornings just from living under air-conditioning here
)