The Apps module is based on the Open App Standard (OAS) and serves as the primary tool for implementing the standard.

While there are many areas of functionality that might be handy for app developers, not all will be appropriate for the Apps module. Not all, for example, will be in line with the explicit interoperability commitments in the standard. A current API change suggestion for which these questions arise is #1730160: Allow themes to be included in App.

If API changes are added to Apps without accompanying changes to the OAS, the two will become increasingly divergent and it will become unclear what parts of Apps are relevant to the standard.

Yes, requiring a change to the OAS for API changes would necessitate more discussion--but this is a good thing.