I tested the building_present_min_level and I'm sorry to say that if you have a line like this:

levels 1 2 3 4 5 6 7

with the upgrades 1->2->3->4 and 1->5->6->7 and give 6 a building_present_min_level 4 it can be built :(
That's not necessarily a bad thing. What would be good to know is that if we had some other building with the condition building_present_min_level 4 that would be triggered by having building 6 in the settlement.