I had the same confusion as the GP. Most people are familiar with the triple point of water, and in particular with the gaseous phase of water in a phase diagra

I had the same confusion as the GP. Most people are familiar with the triple point of water, and in particular with the gaseous phase of water in a phase diagram which is missing here, but it does show prominently in [2]. However [2] shows the pressure in log-scale while this article shows the pressure in 2 linear scales, one from 0 to about 2 GPa and one from 0 to about 100 GPa. The vapor phase which is below 25 MPa in [2] is then compressed here in an invisible slice.