District line does not have those trains, as these trains are aimed at the (much smaller) deep level tube tunnels. The subsurface lines have the luxury of much more space for air con, wider tunnels to carry away waste heat, and sections out in the open.
I think he was referring to the S8 stock currently on the Hammersmith & City, Circle and Metropolitan lines (and being trialed on the District line https://twitter.com/jamescun/status/516498515963695105) which have air-conditioning.
