Although the symbol is clearly different from the regular attack bonus buildings, I have to admit that it could need some kind of description ingame - especially for those that do not read the announcements
lots of folks requested such a building... also attack vs defense is by far not balanced (offered buildings wise) there are far more attack buildings than defense ones - also the attack GB with Zeus, CdM, Aachen, Kraken, AO and Virgo are also dominant in numbers vs. Basil and Deal Castle... did I miss one?
AO is on both sides. Kraken is limited charges. Virgo doesn't even work against the hood. Terracotta is also on both sides (you missed it on both).
Yes there's one more attack bonus GB than defense - but there should be because if people aren't attacking, there's no point to the defense building. And people won't (and already mostly don't) attack unless they have a reasonable shot at winning and there's a payoff for doing so. Most of the big shiny event rewards aren't plunderable. Mars goods buildings aren't plunderable. And now they're throwing extra carrots to people who are bothered someone might take their 20000 coins.
Sure people have asked for attack to their defending army. People have also asked for defense for their attacking army. It doesn't mean we should get it.