Time and complexity really, to add a view like this for Foundation we need to update the API to work with more flexible layouts… so we’d need to create new APIs, maintain both for some period, then deprecate old ones.
Horizon is more of a clean slate, has more limits on customization, and by default lacks some information like tags in the topic list… so it was easier to prioritize without worrying about backwards compatibility. Ideally we’ll take what we learn from Horizon and use that to update Foundation too.
Sorry you’re right, that was a bit off… it doesn’t literally enable that site setting… but it does the same thing (serialize excerpts) only for the theme using a theme modifier