This is an interesting question. I tend to see the ux as a weak vowel as opposed to a strong vowel, which would create a new syllable and changing the stress of the word. "Laux" is pronounced as a one syllable word whereas "Lau" should be pronounced as a two syllable word. Using the cxapelo is mainly for providing a varied pronunciation of a consonant.
I see the logic in it, though, I'm only inferring and have no concrete sources to back up my reasoning other than a personal inference that makes a great deal of sense to me.