Hithere
No, it is not true.
Several things have to be taken into account - all generally speaking and of course not every family works this way
1. The education in the west generally promotes more closeness with daughters than sons, therefore when they grow up, the sons dont call for mom as often as daughters
2. Adults now are much more independent than previous generations, getting the information needed from docs, internet, peers, etc., not relying on the family elders
3. Families now do think "accepting help" isn't choice and can say no
4. Past relationship with parents will lead the relationship when kids come - not where the dna comes from (paternal or maternal side)
5. Women now reject the concept of social secretary, so the paternal side gets left behind if the son does not take care of that.
6. The concept of family has also changed. Core family is protected and grandparents are extended
Family events such as weddings, birth of children, where to live, etc.- are private for input only in the core family
7. Having a child is now rightly seen as a medical event, so the mother and child need to heal and rest.
Their needs become primary and everybody else's wants do not matter.
I think Hithere sums it up pretty well.
My mum is close with my brother's children, and although my SIL is lovely, I think a lot of their closeness is my brother facilitating the relationship, as it should be.