You say "they are" as if this still is the case. Do you mean that installing Tesla shingles give a lower ROI than installing normal shingles and solar panels on top of them?
I can not imagine so. I don't know any other industry where this type of "combine two products" is the better approach. In theory, a single system should always give a better ROI than combining two systems that are not made to be combined in the first place.
Tesla's solar roof is more comparable to expensive slate tiles then the standard tar shingles. Here is an analysis that finds tesla's solar roof is significantly more expensive than a new roof + a traditional solar installation.
I can not imagine so. I don't know any other industry where this type of "combine two products" is the better approach. In theory, a single system should always give a better ROI than combining two systems that are not made to be combined in the first place.