they are telling me to make a 2L starter for 10 gallons of lager 
It's not too far out of line. If you figure that 0.75 million cells per mL is an acceptable, low end pitching rate, it calls for 360 Billion plus for a typical 10 gallon Lager. A 2 L unstirred starter should give you close to 300 billion cells from a fresh pack of yeast. I'm not sure if that's ideal, but I'd expect it to ferment out fine, most of the time, especially if you ramp up the fermentation temperature to help keep the yeast active.
I'm sure you'll see a lot of reports of that rate fermenting out to make great beer. After all, plenty of brewers have made very good beer with a vial of yeast or a vial and a pint or 2 starter. Sometimes the stars don't align and they have problems, though. This is similar to Ken's old procedure and the reports are that his beer was quite good, but every once and a while he would post about this or that off flavor.
One million per mL gives you a little more insurance for a Lager, which could be helpful if you are going to ferment cold and leave it cold. To get there, you'd need to use a 4 qt unstirred starter for 10 gallons. 1.5 million per mL, the more aggressive Lager pitch recommendation would be about what would be expected from a typical Drauflassen of 2+ gallons for a 10 gallon batch.