Oh that's interesting. You probably still need to jump through hoops to figure out the right url for the grid square and level of detail you need. And the session parameter - so you still need to make the initial tile request to get the JSON.

They’ve built a set of framework-agnostic loaders to help sort out which tiles to request for any given viewport https://loaders.gl/docs/modules/tiles

All of the data loading and parsing can be done in loaders.gl, check out the repo 3D-tiles examples for a good place to get started.

You presume I'm doing this in a browser. :-)

I'll have to parse the json myself but it looks doable.

Do a little googling and you can probably find code on github to take care of the "get me terrain for these coordinates" part for you. That's how I managed it a few years ago when I was programmatically downloading tiles from google earth without understanding how to convert from coordinates to their url scheme.

Might have to wait a week though.