The use barriers of the feature are not particularly high. Google officially requires Chrome OS 70, Android 7.1, a data plan with anchor support and the same Google account on both devices. This could change with third-party phones in the mix, but it is a positive sign.
This does not seem to be available in a universal way, and you may need to enable an indicator (chrome: // flags / # instant tethering) to work. In addition, it is unlikely to reach a stable version of Chrome OS for a while. However, it could be a big problem if you like the idea of a Chromebook that is always connected and, preferably, it would not jump through the hoops just to stay online.