Tony, what you're seeing here is the way the feature is coded to work - since some folks with OmniFocus on their iOS devices sync over slow (or expensive) cellular connections, the due date reminders for the next 2 weeks will be published, but that's all.
Since every sync - of each device - pushes out a copy of that file, a larger calendar file that included info on every task with a deadline would very quickly eat up a lot of data.
Pushing out two weeks worth of reminders gives even folks who sync infrequently a good long while before they have to worry about missing a reminder when it comes due, but doesn't eat up a ton of data.
Obviously, the amount of data that gets pushed isn't as big a deal on the Mac, but trying to write/test/keep working properly slightly different versions of the same feature doesn't tend to work out well in the long run. ;-)