Musk's pauses indicate to me that he was internally asking himself whether his proposal is somehow like the Jetsons tubes. That doesn't necessarily mean he was looking for literal parallels. And if he were, I don't see why "pneumatic tube that sucks a single person up" would turn into just "tube" to a layman, either. He's also mentioned the Concorde and a railgun. How do those fit into your vision? Will a layperson see those in your car/tunnel system?
I'm not just saying "pointless complexity". I'm telling you why it's pointless. Your system is certainly more complex than an evacuated tube, and without a compelling reason to embrace such complexity, then it is indeed pointless.
Let's step back a bit, though. You're saying that your system is easier to implement than an evacuated tube. Let's assume that's true (though I don't think it is). Is it also easier to implement than a partially evacuated tube? Those are expected to travel at or past Mach I, and don't need the car to move nearly 100% of the air in the tunnel. How is your proposal superior? You talk about using the plungers to evacuate air, but the energy cost to remove the air must still be paid. Your 70 ton slugs might carry more momentum, but a car in a partially evacuated tube wouldn't need to displace all the air it encounters, and so wouldn't need as much momentum. You're constantly paying the cost to push around a bunch of air. That cost is largely avoided with a more traditional design.
I'm not certain about your idea that you don't need a tight seal. Yes, at Mach I a gust would blow pretty hard. But in a near-vacuum you'll not be blowing much air. Remember that you're going to have to blow with >1 atmosphere of pressure to push anything out and past the flaps. Also remember that this "gust" is the result of resistance caused by the giant plug you're pushing down the tube, resistance that another design might just avoid or at least minimize. And any air not evacuated by the "gust" will contribute to further drag as the plunger pushes past it.