To reply to the OP:
As others have said the Steam client may get the update slightly behind the Frontier launcher but the speed it updates is lightyears ahead compared to the Frontier launcher.
It feels like it reinstalls the whole game everytime it updates (steam takes under 5 mins, Frontiers takes a minimum of 25 mins I find)
Thanks - My question was essentially if Steam gets the update as soon as the servers go off-line and then wander from player to player saying "Here's an update for you" or if Steam had to wait for the servers to come on-line before they're allowed to even start handing you the update. Turns out they have to wait until the servers go live first.
As stated in the OP I'm on DSL so my update takes several hours (depending on the size - Q2 and Q3 weren't that big but Q1 was huge and I expect Q4 is big enough where I should go cut the lawn all day, have dinner, watch a movie, and at 11 PM go to bed and by breakfast the next day it'll just about be done).