That's the client pulling, not the server pushing. Pushing would be "when the owner makes a change on the website, notify the appropriate thermostat to change its settings". This would be way more efficient, but too many Nests aren't going to have suitable internet connections.
Perhaps you misread "yet" as "yes". I'm curious if there's a power issue as well. I don't know how fast wifi can turn on/off and reconnect to a network. Nest has to be low-power as its only power source is one of the tiny wires from the HVAC system and that doesn't supply enough to run the device offline, let alone online. It uses that wire to charge an internal battery instead.
