cisgender, meaning the gender that society and you yourself percieve, is a redundant term.
For someone who believes gender to be a social construct this should be obvious but even to a sane person the concept of gender already embodies your biology and cultural identity. Transgender people are different, hence the prefix. Cis is a way of saying non-trans that stigmatizes transpeople.
I believe alot of transpeople like the new prefix but that’s just feminism talking imo.