I didn't say you should breed them at that age, I was simply stating that the females become sexually mature at 4 1/2 to 5 WEEKS of age. Not that you SHOULD breed them, but it is possible. And for the record, I HAVE seen a 6 week old rat get pregnant. It was not good on her and all of the offspring died.
So...yes...I stand by what I said. You should not wait any longer than the 4 1/2 to 5 weeks to wean. Longer than that and you run the possibility of that happening.