I didn't just invent this model, it's used at Ben Gurion in Tel Aviv.
The checkpoint screens take a few seconds each, they aren't reading you a long prepared statement and checking to see if you respond yes or no. They are looking you in the eye and asking you about your day; they are trained to pick up on your reaction and filter through lots of people quickly. This doesn't move the line outside the airport, as you suggest, it divides the crowds into smaller pools of potential victims and creates "rings" of security. If a terrorist detonates a bomb in the outermost ring, they will likely take out themselves, the security officer and maybe the vehicles immediately adjacent. Worst case, 10-15 people MAX. If the same terrorist makes it to the security line on a holiday weekend, how many people are within the blast radius? I think 10-15 would be a minimum.
As I said in response to the comment above, I'm more of the opinion that the risk/reward equation for a terrorist attack on an airport has shifted and the September 11th attacks would be very difficult to replicate. The passengers on three of those planes assumed (like we all did) that hijackers just wanted money, or to make a speech and that smartest move was to let the authorities deal with it. No one will make that mistake again.
Today's terrorists (homegrown or otherwise) want to maximise casualties, and leave the speeches to be found after the fact. The best way to handle this is to screen and isolate, or to accept that such attacks represent such a statistical minority of deaths from violent crime and spend our security money elsewhere.