Thanks @BrianC!
On the parent staying updated: the skills track Discourse’s theme and Blocks APIs, so as long as we actively use them, they will be kept in sync as the APIs evolve. The example theme is more of a snapshot to demonstrate patterns. If you fork it, you own your fork. But you can refer back to the skills or new examples when updating your theme.
A central goal for the Blocks API itself is a stable, small surface area, that helps keep customizations resilient across Discourse updates. So If you mostly add custom blocks (as the example theme does) you should already operate within a stable environment. The main thing to watch for would be changes to outlet names or block API signatures. Right now the API is still considered experimental, so there might be changes to names etc.
I’d put the recommended approach like this: fork the theme freely, and lean on the skills docs as the living reference for how things should be done going forward.