Here's the deal, I believe Whitelabs provides general info on pitching one vial without a starter. In that case, you would need the higher temp to help in yeast production and still be underpitching. Pitching a large starter allows you to pitch at lower temps, allowing for cleaner flavor. Also, pitching at ferment temp makes it less likely that the yeast will poop out on you from the temp drop.
I agree. White Labs makes a great product, but they sort of lie when they tell you how to pitch a lager. They tell you to pitch warm to compensate for underpitching so hugely, but if you read their website, they recommend against it!
The best "cleanest" lager will come from a HUGE starter at just under fermentation temperature. That means 4-5 packages of yeast, or a 2 gallon starter, and pitched at 45 degrees or so.
When you make an ale, do you add the yeast at 90 degrees, and then lower the beer to 65? No? Then why would you pitch 20-35 degrees too warm with a lager, which should be cleaner and crisper? (By the way, I know some people DO pitch their ales too warm, too, but it's not a good way to treat your yeast).
Pitching at 70 degrees to compensate for gross underpitching usually has some issues with it- first, if you wait until the signs of fermentation begin, and then lower the temperature, the vast majority of primary fermentation will be over before you ever get to 50 degrees. It takes a long time for 5 gallons of fermenting wort to cool! Secondly, it's hard to "catch" the yeast between reproductive and anaerobic fermentation stages, as it doesn't begin/end but sort of flows into the next stage. Third, flavors are created during this time and sometimes the sulfury notes, esters, and diacetyl created by the lager yeast at a too-warm temperature don't fade. And lastly, stressed yeast itself produces off-flavors. One package of White Labs in a 5 gallon batch of a lager is underpitching, which stresses the yeast, plus the temperature changes will also stress the yeast.
If you've already made the lager, it's best to just carry on and give it plenty of time to clean up the off-flavors created. But if you haven't made it yet, make a starter right away so at least you can have some yeast reproduction before pitching the yeast.