Yes, Leap 16 image works differently and it needs the different kernel argument to boot from an ISO image instead of raw device. Posting it here again and again will not change anything. Someone needs to fix Ventoy to support Leap 16. Submit a bug report (or even better a patch) to Ventoy.
Just pass iso-scan/filename=path/to/the/image.iso kernel parameter and Leap 16 image will automatically probe all filesystems for this file and mount it.