CCP Greyscale has sneaked something into the coming Crius release, and it's a long overdue change:
We changed a >= to a > so the code does what the authoring was always assuming it did. I just fixed the display text for the attributes this afternoon to reflect this, but the code should already be in place.
What this means is that moon mining can now take place in 0.4 systems and lower instead of 0.3 systems and lower as is currently the case.
Looks like a simple logic change has finally happened, well overdue and I can see a lot of 0.4 systems will be getting an audit of their moons.
Thanks to Serpentine's EVE for the heads up on this change.