NCAA Libero/Wrong Server

[Scrapper1]

This situation and ruling was part of the most recent Rules Interpretation Newsletter:

Situation 2: The Team S libero has not yet served in the current game. Player S2 (the second server for Team S) should be the next server. However, the libero who has been on the bench, replaces player S5 and goes to the service area to serve. The officials allow the illegal service contact to occur and call the rotational fault. The second referee informs the Team S coach that the libero may only serve in that position.

Ruling: The libero has not yet legally served in this game, and may subsequently serve in any position. But if she serves, she must serve for the next legal player -S2. The scorer should indicate illegal service with a square in the scoring section of the score sheet, and not place a triangle around the “2” under “Service Order”. In the sanctions box the entry should be “L/5” in the WS column.

But on the exam this year, there was a question about the Libero coming to serve. After the beckon for serve, she realizes she's not supposed to serve in that rotation. She allows 8 seconds to expire and her opponent is awarded the point. The answer was that the Libero had to serve in that rotation for the rest of the set.

So I'm confused about why the Libero in the new Interp is not restricted to the "2" rotation. In neither example did the Libero legally contact the serve. So why is the test-question-Libero stuck with her serving spot, but the Interp-Libero is not?