Usually, if someone said QSL via QRZ, it means the QSL information posted on the qrz.com personal page. QRZ not have QSL buro etc
Look at the bottom of his QRZ detail page as it gives you more options. If still unsure, then send him an email and ask him what he means or what his preferred method is.
It mean that he upload QSO to QRZ logbook. It is confirmation of QSO which valid for QRZ award , but really not paper QSL.