Ditto to both B and B.
I like a foiling/braising component to ribs and brisket--but am not a fan of foiling butt during cooking (unless absolutely necessary--like the in-laws have just called and will be 'surprising' you two hours early).
My issue with foiling butt is less of a bark thing and more of what-it-can-do-to-the-rest-of-the-meat-thing: Imo, some somewhat substantial evaporation/dripping of internal moisture/rendered fat and tissue is necessary for the best texture at the finish. Foiling during cooking negates this. (Others opinions may vary, of course.) I prefer to add a vinegar-based finishing sauce--a splash at a time--during pulling, to tie in and add a bit of homogeneity to the finished pulled pork. Foiling during cooking (again, imo), can hold more moisture, but this seems to make the flavor of the finished product less distinctive--more 'watered down'.
With ribs, being thinner and nowhere near as fat-striated or connective tissue-loaded, foiling (imo, at the end--not in the middle--of the cook, for best results), can in fact retain key flavor variables as well as moisture and, if adding flavored liquids to the foil, can add flavor layers as well. This is not possible with butts due to their size--one is only trapping moisture, something that really isn't required because of the higher level of moisture (i.e., water, soft fat deposits, connective tissue) already present in butts.
If the finished results of butts are too dry or not tender enough then they are being overcooked or undercooked. Revamping the approach and the target finish will fix this. Foiling is unnecessary.