well you have the non-PR anomaly for children born before 2003. so for odler children it is not true that PR is automatic.
i agree with snorbs in that i think that where a judge/court orders sole residency it is usually (or should be) because of specific isues - raised in court, reprots from CAFCASS etcetc - whether severe MH (i mean severe and ongoing ); addiction; criminal behaviour or otherwise behaviour which means that the children will be best served with one sole person in charge.
i do think this implies day-today decisions rest with the person with sole residency. for very good reasons eg the other parent is not up to decision making for one reason or another. (my exp in "good" phases makes rash and ill thought out decisions... in bad phases is unableto decide anything...)
i think that in "normal" separations eg due to person going off forming new relationship falling out of love etcetc - then shared residency/shared care makes sense - going off with someone new doesnt necessarily imply inability to parent. breakdown of marriage/relationship in that scenario is comepletetely different to abusive relationship or where one parent has severe and significant issues around MH/addiction/criminal behaviour which makes them unable to parent without input from professionals... (and if things improve that could change later)
i also think that the idea that both parents are involved in every minutiae of decisions in normal circumstances is flawed - where parents are together i would suggest that sometimes each parent takes a role in decisions eg school, researching, deciding -then maybe presenting the conclusion at which parent A says great decision! one parent leaves certain things to the other there is tust they wil make correct decision - prbably because they toegher due to shared values etc. in other cases both may be fully involved every step. that once sperated suddenly parent B wants to be consulted on every last issue -that s/he wasnt that interested in before - well it may seem to be obstructive..
taking the analogy of parens who are together but by circumstance apart - i cant see discussions on limited time sat phone to afghanistan over every last detail of which body part is pierced or not - or even which nursery is chosen - rather there is enough trust that any decisions made will be fine for both. it is about trusting the other parent... some decisions yes need joint agreement.
of course separation may be because one parent has changed their values (eg my exp has suddenly become religious since separation and wants to take DC to sunday school - i dont agree - if equal PR etc then whose decision is it? he has them religious on his days and i have them aetheist on mine? )
the theory of shared residence (equal legal standing) and, where practicable, equal time with each parent is reasonable for sure - and contact blocking should be stopped. the asumption that father and mother are equal is the starting point for sure.
but that this could then be used as stick and argument over every last ear piercing or haircut is not the intention, surely?
but there also has to be mechanism to look at needs of the children where there is abuse/severe MH/criminal behaviour etc. by either parent.
(by severe Mh i dont mean mild depression - but i do mean significant evidence of inability to parent, this would not necessarily mean for example PND as usually that is self limiting and with help the mother gets over it - but during time of severe episode clearly it may mean the father has to take the responsibility, perhaps for older child(ren) while nother is treated. what i mean here is evidence of severe episodes and inability to care for self and others. or where drug/alcohol addition is so severe and person is not following adequate programme. .
where it becomes muddled is criteria and threshold for things like alleged abusive behaviour/what constitutes severe MH/addiction/ etc .
and those situations where it seems that the abuse is directed between the two adults but individually apparently each parent can parent well - so long as the other parent is not around. this "s/he is a good parent" despite the fact they beat the other one up scenario - to me that is where it looks muddied. and where "but i want my fifty percent" is used to beat the other parent.