I just found an article on ZAKZAK that had a few more details on Matsuzaka's bullpen session.
- Matsuzaka wasn't feeling very satisified with his bullpen sessions and decided to go over his 70+ pitch limit today.
- Matsuzaka feels he's still respecting the wishes of the Red Sox by keep his session to 100+ pitches. Back when he was with the Seibu Lions, he often had 200+ pitch bullpen sessions around this time of year so in his mind, 100 is nothing compared to that.
- The Red Sox are extemely worried about Matsuzaka's work-load and are trying to do whatever they can to ensure he doesn't throw too much.
- Matsuzaka is required to provide detailed information regarding his workouts. The Red Sox also apparently have someone pouring over the Japanese papers every day to see what's been said through the media.
- WBC Pitching Coach Hisashi Yamada said, "Matsuzaka just loves to pitch. I'll let him decide how many pitches he wants to throw."
- While not 100% clear, it does appear as though Matsuzaka got permission from the Red Sox to throw 100+ pitches. The article uses the word "譲歩した", which translates to "made concessions / compromises," but doesn't really go into any further details.
As Mike mentioned in a comment, it'll be interesting to see what happens if Matsuzaka hits a wall during the middle of the season. If he does, the Red Sox definitely aren't going to be happy.