As others have said, hair properties are much more important then curl type for choosing ingredients/products. Curl type is transient. Before I came on nc.com and learned how to use product/technique, I was a winter wavy/summer 3a. Now my hair looks like my signature picture every day, all year around.
The only place that I've read about low porosity not liking protein is on the nc.com hair property page, which is why I don't use that link when suggesting people determine their properties. My fine/low porosity hair never met a protein it didn't like. I do at least one PT a week and use a lot of products with protein. For me, it reduces frizz and tightens curl.
3a (Corkicelli), highlighted, fine, low porosity
modified CG, since April '07
CG since 3/11/08
HGs: Curly Kinks Satin Roots, Curlycue ReNew and Coil Jam; homemade FSG and okra gel; soap bars; DM MiraCurls Curling Gelly; UFD Curly Magic; Shescentit LIs; Sevi conditioners; Botanical Spirits Puree, CJ Repair Me