Orca
The "high" risk designation was for the whole engagement risk, one on one I would put Fast jet vs Truck mounted AAA gun(s) as low risk to the jet and the upper end of the opposite scale for the truck.
The problems come with the remainder of the environment were there are likely to be other AAA assets and may be MANPADs, add to this the danger of any crew who escape from a damaged aircraft are likely to be staring on Utube alongside a well known knife owner from south London and this puts physical/ political risk is at the high end of the scale.
Politicians see the Brimstone in the same way as the Gatwick airport management see forcing me to don a hi-vis vest, it lets them say " I mitigated the risk" and so they can go about their daily business without fear of critics who might damage their carreer.............. Yes the last paragraph is a little tongue in cheek !