I think both of those reactions are taking continuity way too far, using continuity to hurt storytelling rather than help it. I don't think it matters that one episode had Kirk with a much younger rarely thought of brother and likewise doesn't matter that a little over 70 episodes and a few more films didn't establish that Spock had a brother, why would they, must they have, it at least made sense, was plausible when the half-brother was estranged and Spock rarely talked about his family, personal life at all anyway.