Also, just wanted to say I found more information on Exfoliative Chelitis in HIV patients which supports the xerostomia/dry mouth/lack of saliva hypothesis for EC.
This quote is taken from a paper called " Oral Manifestations of Paediatric HIV Infection " which shows pictures of a HIV patient with crusted lips i.e. Exfoliative chelitis
which the article describes as "Dry lips with crusting, resulting from xerostomia"
; "Xerostomia is a common symptom of HIV-infected individuals and has many potential causes. It is more common in HIV infected children than HIV-infected adults. The causes of xerostomia include HIV infection itself, therapeutic antiviral and antimicrobial drugs, prophylactic medications, antiretrovirals (such as didanosine), gamma globulin, or lymphocytic infiltration of the major salivary glands. Clinical features include dry mouth (Figure 16) and severely reduced salivary flow rates. Reduced salivary flow results in a mucosa that is desiccated and is at higher risk for opportunistic infections such as candidiasis and increased caries. Xerostomia may appear with or without parotid swelling. No definitive diagnostic criteria exist for xerostomia. (Flaitz & Hicks 2003; "
Look at the pictures in the article. Note how they look exactly like EC (Are in the same place as EC crusts)https://www.researchgate.net/figure/221919824_fig11_Fig-16-Dry-lips-with-crusting-resulting-from-xerostomia
IT could be that EC results from some combination between xerostomia and lowered immunity.