The interpretation of IP law, at least internally at many big software companies, does in fact work like coodies. Hence things like "clean room implementations" of algorithms, modules, API interfaces etc.
Clean room matters for copyright. It doesn't help for patents, as patents protects the idea, not the expression of it so expressing the same idea in a different way doesn't help. With a patent you want to know the specifics of the original to ensure you make yours sufficiently different to sidestep the claims.
Where not knowing helps with patents it is in that if you infringe, wilfull infringement increases damages up to threefold.
