IsItMeOr thats interesting - we're doing BLW too and that is leaving them to it, you're right. I suppose you sit with them though, and do the odd bit of exagerated chewing .
FWIW, I am now, because it feels natural, leaving my DS (almost 7 months) to settle himself completely, after bath etc, but I respond pretty quickly if he makes an 'i'm not ok' noise. I then help him out. I tried one night to leave him to grumble for longer but his stress level was rising, not falling - he was getting more and more irate and when it turned to crying, I was happy to go get him. So now I don't see the point, I might as well leave him if he is happy and calm, and stay and help if he is not. He needs me less and less, and gets more and more independent. Maybe I will feel differently when he is 13.5 months - I am definitely not saying it is never appropriate.
Different babies though too - I suppose I am doing what feels right in this situation, with my DS who has a particular type of character.
Undoubtedly though, the thought of young babies crying alone, quite distressed until they give up, in a bid to get them to sleep to a prescribed timetable is, IMO, actually quite upsetting.
(Getting a bit carried away now )