Barriers to resource use are not particularly high. Google officially requires Chrome OS 70, Android 7.1, a data plan with support for tethering, and the same Google account on both devices. This may change with third-party phones, but it's a positive sign.
This does not seem to be universally available, and you may need to enable a flag (chrome: // flags / # instant-tethering) to work. It's also unlikely that you'll be able to reach a stable version of Chrome OS for some time. However, it can be a big deal if you like the thought of an always-connected Chromebook and prefer not to jump on the hoops just to get online.