DH-10 cruise missile

Angle of impact is probably more accurate and intuitive, since angle of incident is usually used to measure ray effects and is measured against a normal, which is needlessly complicated and potentially misleading.

90 degree angle of impact means the missile was coming in near vertically down. And probably corresponds to the image of the building with a big hole on the roof.

Such a capability is useful for taking out bunkers and other underground targets.

I'd bet now after US has left INF more DF-10s are going to become nuclear armed and numbers of cruise missiles is going to increase.

Do HN-3 missiles actually exist or is it just an different name for DF-10 series? Googles picture search shows HN-3 missile what has "stealthy body" and others show something what looks a lot like DF-10 but little different.

I think its just a different, earlier name of the same cruise missile family, which also goes by the CJ letters. DH appears to be what is currently used.