Not at all.
When you first start wearing your huaraches, you’ll notice it somewhat. After all, it is a thing. But very quickly the sensation fades into the background.
Also, you can change the tightness by the way you lace your sandal. If you loosen the heel, your foot moves further back and takes some pressure off the string. Or, obviously, you can loosen that “foot string”, or change the placement of it by tightening/loosening the loop that goes around it.
Plus, there are ways of tying Xero Shoes huaraches that don’t have a string going between your toes.
Finding the perfect way to tie huaraches is a personal thing, there’s no “one best way.” You’ll find the one that works for you with a couple of tries.