The thing is, there's no standard form in which the MATLAB 'sources' come in. It's bits and pieces everywhere.

I agree this could be implemented somehow, or the separate files could simply be listed instead of forcing to specify a tarball, but I don't see how we can ensure it always works without a manual step like this...

Believe me, I would have rather seen it different...

This should be revisited in the future, e.g. when you're installing MATLAB.