I think an important point to make is that they do hide the gender from pop's environment, not so from pop. Pop has body parts known to him/her which he/she can identify with as self' and being a certasin 'sexe'. Only pop will find out in his/her own time what gender she/he is. And will ask questions about this in the near future anyway ('what's this?' cfr. body parts). Probably will start asking questions about the way people (male and female) dress in her environment. Imo, the 'secret' is only there to other people to avoid them adressing the child in a gender specific way. I personally think it's great of the parenjt's to make a well-thought effort do create this neutral setting for their child. This is elf-determination for the child as when to discover and decide to reveal gender, and only later experience gender-specific treatment by environment but not immediately by birth. I do not think such a way will prevent pop from finding out his/her true 'innate' gender, since I believe part of gender is biologically and genetically determined, and a lot of what is attached to gender nowadays is culturally and artificially determined. I do not think it will be harmful for the child since gender won't be kept a secret from him/her.
Personally, I have always resented the gender-specific treatment of people in society, and it starts as early as they pop (pun not intended
) out at birth (or even before that...). And I have tried to at least stick to gender neutrality/non-comformity cfr. my young children to a certain extent, but I see that even in our family, due to societal norms, and cultural norms, and even due to my own 'accustomed' behaviours/habits/thinking/learned gender specific customs, it's been only succesful for a tiny tiny little bit. As in that pink is a colour for everyone, glitter can be liked by anyone, boys and girls ae free to enjoy any play they want, people of all genders are allowed to cry, rough play and sweetness can appear in both genders, hairstyle's gender specificness is only a societal norm not shared by everyone or every culture, and similar. I also try to make them be conscious about their own language when being judgingly genderspecific, and let us realise what we are saying, and if such is really true, by adjusting texts I'm reading when too gender 'specific' examples that are plain sexist, imo. Etc.