At the moment, yes - we want to figure out the principles of application/block interaction in a web context first, and then move on to other environments. The principles should be transferable, although some of the 'how are they implemented' won't be (https://blockprotocol.org/docs/faq#what-about-non-web-contex...)

The comment above you is right that 'handling blocks implemented in different ways' (in a web context) is one of the mushier parts of the spec, and it's something we need to do more prototyping and refinement of.