The implications of twelver /ithna Ashari belief that fadak was gift /endowment to fatima?

I recently learnt that fadak was an endowment to fatima by the prophet of Islam and abu bakr confiscated it as per twelver Fadak came under prophet/muslims in 628 CE. https://en.m.wikipedia.org/wiki/Conquest_of_Fadak Zaynab bint Muhammad died in 629 CE. Umm kulsum bint Muhammad died in 630 CE. Twelver say fadak was endowment and not inheritance. Even if it's assumed if this is endowment are we accepting that prophet did injustice to zaynab and umm kulthum by not gifting them anything? Is this a slander on the prophet of Islam? I believe quran orders the parents to be just and equal in giving gifts to children.