That does make a lot of sense, that they need to make that disclaimer to retract what we already witnessed. However, there was no such disclaimer on the Thursday show apparently.
The Friday show had the disclaimer when the show ended 2 questions into the first round, which was rebooted on Monday with the same challenger.
I think it would have been tidier to call out the disclaimer on the other episodes, too, particularly since they had the time at the end for a regular read. But, it is also possible they overthought this ... if the viewer hears they declared someone ineligible on Thursday, does the viewer wonder why the champion comes back on Friday? Also, they might have felt that announcing a player is ineligible the day before, the viewers would know the result is a wipe. Again, a lot of overthinking, and obviously the suits went over all the options with S&P.
As for the disclaimer being necessary after Bob revealed the ineligibility: that is a boilerplate statement that continues to this day, mentioning which player is ineligible and they would not receive the prizes. Because Bob didn't cover all the legalese, that's probably what lead to the decision to insert the voiceover on the Friday show.