Why double fry French fries after blanching instead of just blanching and frying

I love good fries fries. I've made them with some success at home using the Steak Frites recipe originally developed by Cooks Illustrated/America's Test Kitchen. In their recipe cut potatoes are rinsed, soaked, fried at a lower temperature, then finished at a higher temperature. It did not involve blanching, and I've been convinced through research that blanching them can be helpful.

In another recipe I've found for twice-cooked fries, they are merely blanched and then fried. Is this technique going to produce good fries?

According to Serious Eats fries from McDonald's are both blanched and fried at a lower temperature, frozen, and then finally fried before being served to you.

The French Culinary Institute has a technique that pre-blanches, blanches, freezes, and then twice fries – talk about work!

From what I've read pectin is released during the blanching at certain temperatures. Also the blanching removes some external starches, which I assume rinsing and soaking may accomplish. Plus if you blanch in salted water you pre-salt the fries.

My question is, what does that initial lower temperature fry do? Cook the inside? Why should I do it instead of just blanching and frying once? The accepted answer to this question says the initial fry is to cook the fries, which it seems blanching already does. It seems to have something to do with starch molecules, but I'm interested in the details.