Properties of observed disks. The left and right panels show the histograms for cold gas fraction, f, and redshift, z, for the VELA disks in red and the Genzel et al. (2023) galaxies in green. The VELA disks span a wider redshift range and have typically lower gas fractions than the Genzel et al. (2023) sample. While the lower gas fractions in VELA could potentially bias our conclusions, the simulated sample does include a few gas-rich galaxies. But the disk-averaged radial velocities in even these gas-rich galaxies barely reproduce the observations, which are much better explained when assumed to be originating from recently accreted streams.