Hmm it's an interesting idea, but what is a parent to do if their child hates lying down. For the first 5 months, DD hated, hated being laid on the floor, both on her back and on her tummy. (It was only after starting osteo treatment that she started to enjoy it). She was able to lift her head (briefly) from birth and has always preferred being upright. People often commented on the way DH and I would hold her. It felt natural to hold her upright with her head resting against our shoulder and she was happiest in this position. She also preferred reclining against our legs facing us as we played.

I guess it's not just about baby-led movement, but baby-led positioning too.