A number of different things can be true.
I can believe that a new mother who has a male partner assertively advocating for her can end up with better treatment than they otherwise would have had. We know that women are dismissed far more than men. Especially in healthcare.
Stemming from this fact individually many women will feel happier with their partner by their side for the duration and probably do benefit, again on an individual level.
Conversely a blanket policy of allowing all men all the time brings with it issues that postnatal services never used to have to deal with.
This ranges from men taking up physical space, adding to noise levels overnight and generally being a bit thoughtless and selfish even if well intended.
Then you have the men who are abusive and voyeuristic, the men who harass their partners about blow jobs and threaten staff and patients.
Most women who want their own partner present could still do without the male partners of other women in their vicinity when vulnerable and dealing with postnatal issues.
The only true solution to this is properly staffed and funded maternity services. Rooms or wards actually designed with the needs of new mothers and newborns in mind and respect for women who have given birth, their mobility needs, their pain management and mental health.
Trying to fix the problems by allowing men 24/7 access to shared postnatal facilities is like putting a manky bandaid on a big cut. It might stem the immediate bleed but could give you sepsis.