So after all the question I asked wasn't dumb, nor was it a new questipn 
Super dumb question about a rule.
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So after all the question I asked wasn't dumb, nor was it a new questipn
The problem with saying a pinned piece doesn't threaten squares runs into some serious problems if you extend the logic out a bit. For example, in the setup below:
That's an interesting position to illustrate what might seem problematic with the rule that "pinned pieces don't check", but there's nothing actually wrong or logically inconsistent with such a rule. Ultimately it's a matter of convention which rule we decide to use (and I'm happy with the existing one). So in your position, The WQ-BR pin means that the BR doesn't check on the c-file, so if the WK is on c5, the WB is free to move, which means the WB DOES pin the BN, and the latter doesn't check the WK on c5 - therefore 1.Kc5 is legal. Now if there is no WQ on a8, then the BR DOES pin the WB, which is thus unable to check, and that means the BN is free to move and check the WK on c5 - therefore 1.Kc5 is illegal without the WQ.
Such convoluted "pin logic" is explored by problem composers as a matter of course when they use this rule, called "Superpins" as mentioned above. For an example of a Mate-in-2 problem that uses this rule, see this position by the composer C Sydenham (in the solution, S (not N) = knight).