OSPF import policies only allow the filtering of external routes.
In the import statement, you list the name of the routing policy used to filter OSPF external routes from being installed into the routing tables of OSPF neighbors. You can filter the routes, but not link-state address (LSA) flooding. An external route is a route that is outside the OSPF Autonomous System (AS). The import policy does not impact the OSPF database. This means that the import policy has no impact on the link-state advertisements.
Like spuluka said, you can only filter external routes, so your existing policy only applies to the 10.18.70.0/24 route. The other subnets mentioned in your "allow" term will still show up in your table even if you remove them from the term because they are not external routes.
I'm playing around with stub areas. It has the desired effect of external routes not prorogating. The problem is that the routes from the stub area aren't being prorogated to the main area. For devices in the main area, I'm seeing a summary route to the interface on the adjacent device in the stub area but none of the routes in the stub area. Is there something I need to do to get stub area routes advertised into the main area?