You could see that you have only 7.6G for rootfs.
From your XML…
sector_size="512" num_sectors="122159104"
The size for NVMe is 512*122159104 = 62545461248 = 58.25 GB.
Please note the following:
physical size >= sector_size*num_sectors > -S parameter
The physical size of your NVMe SSD is 945.57GiB
If you want to have 500 GB for rootfs, you could use -S 500GiB in your flash command, and modify num_sectors to 1073741824, which resulting 512*1073741824 = 512GiB