No, grass matches are much faster and typically Fed won't be on court for more than 80 minutes per match. Also, there is a week of gap between Halle and Wimbledon. So, this is not a bad scheduling decision (like playing in Montreal last year).
Stuttgart remains as the answer to the trivia question "Name a grass tourney that Fed has played but never won". So, it would be nice to have a win there. Further, these titles will help him get to Connors faster (even though the title count of Connors as all of us know is essentially made up of disproportionate number of Small tourneys, almost like Vilas on Clay).
Finally, playing both Stuttgart and Halle, gives himself the protection of actually getting enough match practice on grass, even if he were to lose early in one of them.