Here you don't need to commit anything else than the repo version.
The alternative you're suggesting is
1) clone ol3 fork
2) build it
3) copy/paste the generated files
4) commit all the files

....

At the moment layersconfig files are generated on the fly
https://github.com/geoadmin/ol3/blob/master/build-ga.py#L82

As you can see layersconfig files are based on the api based in prod. This is a problem. If we actually decide to not use submodules, we need to change that.