I found this comment in "base.res_partner_view"

" parent_id and type fields needed in attrs in base_address_city module which overwrites _fields_view_get() of partner. It would be better to put those fields there but the web client dosen't support when a field is displayed several times in the same view "

But I'm able to show two times a field in contact form with no problem, apparently

I wonder if we still have to worry about this practice in Odoo14 or it is just an old comment that wasn't removed yet?