There are also advantages of having a pre-evaluated layout. Namely, that you don’t have to evaluate it on every page load, if for some reason it’s computationally expensive. Although layout generation probably won’t be usually. A more compelling reason I think is that it means you catch bugs in your layout generation on app load rather than when a user visits the site, which makes for an easier debugging experience.
I think the appropriate solution is improved documentation of dynamic layouts. Perhaps this wants to be moved, or just added to the main part of the guide. Arguably this isn’t advanced usage, and including it as another option for building a layout will make it more discoverable.
Also, if there was a FAQ it could go in there. I’ve been collecting a list of gotchas that I see people commonly posting, and have been meaning to post to try to get this going.