I have heard that, to get crispy french fries, I need to get rid of the excess starch on the surface of potatoes after cutting them. But that can't be the reason, really, because starch is actually what FORMS the crust... so my reasoning is the following: we soak them because enzymes released by cutting will quickly convert the starch into glucose, and THAT will caramelise and burn our french fries. Is that the reason why we use cold water, to keep the enzyme inactive?  If so, soaking in cold water seems unnecessary to me. Thoroughly rinsing until the water runs clean should be enough. Am I correct? 
According to https://foodcrumbles.com/should-you-rinse-or-soak-potatoes-before-frying-an-experiment/ when it comes to crispiness it makes little difference whether you soak for a long period of time or not (it only affects the color).  So you are basically correct that thoroughly rinsing until the water runs clean should be enough. 