I found your question interesting, as until recently, it never occurred to me to sew into that fold. Then, while reviewing a tutorial (one on the sew-off method mentioned previously), I saw stitches made into the fold when hand sewing the binding to the back. It made me wonder if I'd been doing it wrong all these years.
If I've been doing it wrong, it still works for me, as I've never had a roblem. I do now take a couple of stitches when doing baby quilts, as it does seem possible that a tiny finger could get into that space.