I'll assume all starters sat the entire 1st half. My apologies if I my guess is wrong. It's tempting because it violates all taboos surrounding The Way Things Are Done.
MM probably did this without a shred of altruism. With MD waiting on Saturday, the starters need to be fresh, but sharp. Limiting them to one half of full throttle work looks like a good idea. Aside from this, the Salesian-BC foulfest illustrated that you never know when your #9 player may need to make a Big Play in a Big Game. Playing the bench exclusively for a half gives these kids extended continuous game experience with no starters around to lean on/depend on/hide behind, a developmental task that must be hard to simulate in practice. Also, no running clock and a close score. Finally, giving minutes to the kids down the bench from your primary playing rotation, without impairing your team's maximum capabilities (requiring the primary rotation to play most of the time) is just the right thing to do.
How do your opponents feel? Well, you can't control how other people feel about your actions. I think that kids who soldier through a difficult season are smarter, tougher, and less thin skinned than some think. A competitive first half might be a pleasant surprise. Sure, there's no free lunch, but there's lunch. You've got halftime to enjoy the meal before paying the bill.
Think of this strategy as a mismatch Productivity Multiplier. Or, if we rated Blowouts like hurricanes, a Category 5 Protocol.
