Molecules have new orbitals, which are different from atomic orbitals. It could be new terms for that area.

I think weather it is organic or inorganic solids , the energy levels should be labeled as VB and CB because there are no discrete energy levels in solid instead these energy levels are close that they form continuum. HOMO and LUMO labeling should be limited to molecule. But in the literature as you have mentioned (eg polymers) energy levels for organic materials (or polymers) are labeled as HOMO and LUMO. I do not know exactly why. I think it might be just a traditonal (conventional) way.

HOMO and LUMO are designations of ORBITALS in separate molecules. The valence band picture in organic solids can be applied, but the delocalization is much less than e.g. in metals. The bands are narrower and more separated (usually). There are exceptions, as e.g. in conducting polymers, where BANDS rathe than ORBITALS describe the situation better. Excitons and other pseudo-particles are also delocalized. I think the the use of HOMO and LUMO by organic solid state physicists comes form the traditional use of these terms in molecular spectorscopy.

The terms HOMO and LUMO are used in context with quantum physics while the terms Conduction band and Valance Band are used in context with Classical Physics. Homo  is analogues to valance band while LUMO is analogues to Conduction band. The difference of the CB-VB is band gap and on similar terms LUMO-HOMO is the band gap and is energy levels required for the conduction to take place. 

https://books.google.it/books?id=CsGg_No81ycC&pg=PA57&lpg=PA57&dq=what+are+the+difference+between+humo++conduction+band+in+inoraganic&source=bl&ots=uw2j21iMt0&sig=cGhPQ-MfIw_rSxGjwHnFa7zdgH0&hl=en&sa=X&ved=2ahUKEwiFjMTn09DdAhWww4sKHbXIBPwQ6AEwEXoECAAQAQ#v=onepage&q=what%20are%20the%20difference%20between%20humo%20%20conduction%20band%20in%20inoraganic&f=false

I agree with Gyorgy. I would like to add a discussion about a similar topic and can be useful for explaining the correlation between the homo and lumo levels in the organic molecular materials with weak molecular bonding and the inorganic material with large assembly of strong atomic bonding.https://www.researchgate.net/post/It_is_required_to_compare_organic_and_inorganic_semiconductors

Best wishes

Molecules have new orbitals, which are different from atomic orbitals. It could be new terms for that area.