Had my Nephew overnight from two weeks old, his Mum needed that support and as long as he was fed and cuddled, it didn't matter to him, who was providing that care.
There isn't a one size fits all when it comes to bonding, a break and rest can be the difference between struggling and parenting inadequetly and overall parenting well.
Women who had PND, were once judged, we now encourage Women to get and take the help they need.
If a woman is struggling for any other reason, then she should be able to ask her Mum for any help she needs and everyone else should butt the fuck out.
If you are generally a judgemental person, they aren't going to share what's really going on.
I saw parents who should of asked and taken the support being offered, when I was a CP SW, there children suffered because they struggled on.
My DD has a month old baby, I'm babysitting on Friday and having her for two nights at six weeks old.
My DD is BF on demand, she has well enough time to bond and has done so.
A baby doesn't bond with it's primary carer in a way that causes Emotional Damage, if it doesn't happen, until three months of age.
Then the care should be consistent, but the baby is able to be left with secondary carers and bond with them, with no lasting damage and the research shows that children benefit from developing a strong secondary carer attachment/relationship.
Every tribe was based on this theory, Grandmothers would look after newborns/infants whilst the Parents went back to their village duties.
This new idea of Mothers being in isolation and children being with just primary carers until people outside the family (Childminders/teachers etc) take over, is a new concept and one which isn't doing our Mental Health any favours.
There is nothing to judge, here.