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The situations are different. In (a), two distinct groups of two are formed, “committee” and “not committee”. But in (b), we instead form two *non*-distinct “team” groups of two each.

In fairness, the non-distinctness of the teams in (b) is not explicit in the question. You could certainly argue that labelling the teams in distinct ways (A vs B, red vs blue, shirts vs bibs) is a valid assumption, and in that case there are six ways to do it.