I think this is sort of a no lose situation as long as he gets his chance to play for a while. If he plays regularly, this should not hurt his development (assuming they have a good psychological read and he can deal with possible failure). If they do catch lightening, great. If they don't, he stays up until Goodwin comes back, the coaches get to see him, he is more comfortable next call up, and they aren't wondering in September about whether his track record is enough to help that month or maybe in October. If he pans out, then Eaton can possibly take center when he is back and you can have Taylor in a deal or as 5th OF. This is a lot more valuable than seeing what you can get out of Moises Sierra. Maybe you are better off with Adams in left and Reynolds at 1st while RZ is out, but frankly, both of those guys are hitting better than they really are.
It's sooner than you would have liked, but there isn't much of a downside.