There’s really so much wrong with this. We can understand why they’re not comparable when you think for even a second about WHY the case you references is a crime.
What harm is it trying to remedy? It’s obvious that providing a child to someone who is not their parent without a formal, legal process to assign them parental rights is fraught with risks for the child. There is no vetting process to ensure they are suitable parents for the child and no record of where the child lives for safeguarding.
That doesn’t apply when it comes to a child being brought up by their biological parent. And if their partner wants to obtain parental responsibility then they need to engage in a formal process to do so.
Thats why if a woman decided to divorce her husband and childrens father - she wouldn’t be criminalised if she gave him sole custody and parental responsibility in return for a larger financial settlement, for example. Because you cannot ‘sell’ a child to their parent!