Wouldn't it be inconsistent to interpret the Strand heading one way and one of its paragraphs another way? 5(c) for example mentions "legislation" without mentioning which body that legislation belongs to. 5 says "all sections of the community are protected" without distinguishing against what.
5(c) is referring to what became HRA s 3 , and I'd interpret 5 (b) as being what became HRA s 6. I don't see the tension. It isn't about the ECHR itself.
5(b) is implemented by s.6 HRA as regards public authorities generally, but by ss.6 and 24 Northern Ireland Act 1998 as regards legislation by the Assembly and acts of the executive. My understanding is that 5(c) is implemented by ss.9-11 to ensure Assembly Bills are scrutanised for compliance.