PIX does have a chargeback-like mechanism. It was introduced a year later its release though. PIX is actually more than just instant payment, it includes other things like Pix Saque (withdraw) and Pix Troco (change).

Src (pt only) https://www.poder360.com.br/economia/bc-libera-mecanismo-de-... and https://www.in.gov.br/web/dou/-/resolucao-bcb-n-103-de-8-de-...