"Maybe I am off base and the work that goes into MU 2.8 would have to be done anyway to get to 2.8.1?"
Yes. If you look at trac, you can see exactly how much work goes into pushing a release. Also, development will slow to a crawl if nobody tests the files in trunk.
We need people to test it *before* a release, so it *can* be released.
And if you haven't heard, MU will be merging back into WP, so there will only be one codebase. So when that happens, this will all be a moot point.