The QR code doesn't open a link. It's just "gibberish" text only usable by app that can understand it (e.g. banking apps).

(I don't know anything about UPI, but in Indonesia we use a similar system)

Its not gibberish text.

Its just a URI.

  upi://pay?pa=payeeID&pn=payeeName

I am Indian and I think what you are saying is correct. It opens up the banking app or in our case UPI providers app so like Google pay, Phonepe,paytm, Bhim UPI and other such apps.