Yes if you're gonna freeze potatoes or fries you must blanch the fries or potatoes before you freeze them.
If you just place the potatoes or fries in the freezer without blanching the potatoes or fries first then they will become mushy when you freeze and cook them.
So make sure you blanch the potatoes or fries before you freeze them if you want them to turn out good after cooking them.
You can blanch the potatoes whole or you can blanch the potatoes after you cut them up.
Blanching the potatoes before freezing them is what the french fry companies do to make them and then freeze them so they turn out proper.