Attila the Hun gets Battering Ram bonus on Rocket Artillery?

I've been playing as Attila the Hun and initially I enjoyed the use of the battering rams and their +200% bonus against cities.

However I am now much further on and all siege units I build also have this bonus. I was under the impression that this bonus only applies to battering rams, however I've been building rocket artillery and they all have this bonus as well.

Is this intentional? Or is this some kind of beneficial glitch in this particular game? *

Not that I'm complaining either way; rocket artillery with a +200% bonus are deadly against cities.

(*) I had a game with a glitch in it a while back, where the number of turns until I get a golden age was incrementing at a much lower rate, meaning that later on in the game when I was generating 50+ happiness I only had to wait 3 or 4 turns in between golden ages. I've never been able to recreate this glitch outside of the save files I have for that particular game. Needless to say in that particular game I had insane amounts of cash. I was wondering if this was a similar glitch.

This is not a glitch. Most siege weapons get the +200% bonus against cities. (Presumably, so they are more effective against cities than they are as imprompteau ranged units).

Battering Rams get +300%, though, which is where I think your confusion might be coming from.

Rocket Artillery