It probably politically made sense at the time - there is no certainty that the SC would uphold the 5th with Partial-Birth O'Connor on the bench. Secondly, if they did uphold it, it would have made it harder for Bush to get conservatives on the SC, as the GOP was in the minority at the time. Just my thoughts.
I also think the 5th is the court that Pickering and Owens wer nominated for - no wonder Herr Schumer and Leahy wanted to keep conservatives off of it. Schumer especially is a anti gun Nazi.