My 2 simple rules for crunch mode:
1. Manager better be there. Me personally, i would dive in and actually start doing code reviews. But even if I had absolutely nothing to add, I had to be there to show support. Even for window dressing. You call for crunch mode, you better be present. Even if its just to buy lunch or starbucks for the devs.
2. Coding is like breathing. Crunch mode inhale must be followed by re-tooling, decompressing exhale. You can only inhale so much.
Your two rules are...minimally adequate, I guess. They're certainly nothing to pat yourself on the back about.
Which is why I can get away with my minimally adequate rules as you've put it. I certainly dont pat myself in the back about my rules. Its all about sharing the pain. I also forgot my 3rd rule. Only developers set deadlines so I can ask them to commit to it. If we have a date to hit, then we work on scope.
Though its usually a nightmare for me to work this out with HR, days off to me can mean actual vacation time which to me, is more precious than cash. It can also mean time doing cool stuff, or as the late Steven Covey would put it, time to spend "sharpening the axe" like making a presentation on the latest version of FizzBangWow product/language/framework, trips to conferences. I've even had devs prefer to work on clearing out technical debt. That's craft.