You are talking as if it's an employers market right now in the engineering field, when it's not (and hasn't been for a long while). I don't know of any large company that does not hire some junior engineers, and projects like this is a perfect use for them. As they have more experience they can work on some more advanced projects.
This is ignoring the fact that with engineering, throwing more people at a problem does not necessarily make the solution come sooner (many times it's the opposite). As others mentioned, suffice to say, the work on this feature is unlikely to have any significant impact on the other features (especially given it was developed for Chinese market first, where it makes complete sense given people can use it to preview a wrap, which presumably Tesla earns a profit on, something a lot of people seemed to have ignored).