I think that you have to recognize that different babies and different parents are different. I had one baby who liked to be swaddled and left on his own to go to sleep, who enjoyed rolling around on the floor and was all in all very independent. He did scream a bit when left to go to sleep, but to a definite rhythm, so that you could pretty much predict when he found his thumb, and when he'd go to sleep (took maybe 5 mins). If you tried holding him during that time he'd flail around and not go to sleep at all, with the result being one tired and cranky baby. With dd on the other hand she was very very clingy, she'd cry for what seemed like ages (not in a screamy way, just persistent) and not only did she want to be held, but she wanted to be walked around (she'd scream in your arms if you tried to sit down, or just stopped walking/swaying etc).
For me, ds was an easy baby, and dd was a nightmare. Now if I'd been a isn't it lovely my baby needs me so sort of person, then I might well have felt the reverse, but I'm not terribly keen on babies (I much prefer children) and I found dd suffocating and frustrating. It's all very well to say that everyone should love to have their child attached to them at all times, but what if you hate that? If you find permanent feeding exhausting and sharing a bed = no sleep at all? I watched my big sister and my aunt take a demand/attachment approach, and saw how totally exhausted they were and thought not for me.
So I don't think it is always societies expectations, after all there is no one way that mothers are told to do things - the one consistency is the inconsistency it seems to me.
Oh and if you want to think about the equivalency to the Bowlby experiment (which should never have been allowed, and I thought the big study was undertaken by Harlow in any case - Bowlby looked at children separated from their mothers in hospital, whereas Harlow removed monkeys from their mothers entirely, and did things like hold them in isolation for years. He seemed to quite enjoy torture too. Totally barbaric - he even referred to himself as a sadist) then look at children who are seriously neglected (think cupboard children or Romanian orphanages) or children who are separated entirely from their families with no loving substitutes (as used to happen if they were hospitalised for any reason, although I think for full attachment disorders this would need to be for significant periods of time) not parents who think it is OK to allow their children to wail for a few minutes before they go to sleep whilst otherwise meeting their physical and emotional needs. I doubt very much that you could tell with an average reception class who had had strict routines and who was "worn" - or everyone in between for that matter.
If you love having your child attached to you then go for it, but don't describe those that don't as cruel or say that your way is best, or make out that her children are going to be deeply scarred. Because for another mother it might be a nightmare that drives her to the end of her tether. Likewise the other way round of course.