Ok, so the certificate used to sign the package is generated by Apple, why can't I just use that to prove my identity for notarization? Or maybe simpler, why c

Ok, so the certificate used to sign the package is generated by Apple, why can't I just use that to prove my identity for notarization? Or maybe simpler, why can't Apple just do code sign and notarization with one single cli call, with one set of credentials? Google Play does this under the hook, I don't even think about it. iOS is similar, Transponder app does everything in one go.