I think it's worth discussing further. This thread says the change is only to further enforce the general policy in place since 2010, but this enforcement could have came day one. Instead, it happens after the first wave of bans in honorbuddy's history. This leads me to assume the following, but correct me if I am wrong.
1.
Allowing the powerful API you get with this bot into the main competitive route of WoW was always a concern of being too harmful/poking blizzard. Support was decided to not be given at all, but not disabled in the hopes not supporting it would be enough to keep blizzard uninterested or at least less so in detecting HB.
2.
If the above is true, you guys should further evaluate the situation. Yes in 2010 arena was the only real concern for you guys in terms of areas of the game your bots API could be used, but the reasoning behind it if I am right now also apply's to more area's than just arenas, as much or even more so I think. The following should be heavily considered to achieve your goals if my above assumptions are right:
-Disable HB functions while in a mythic raid of current content. This group (current content mythic raiders) are often as competitive or even more so than arena, widely viewed in the public eye as well/discussed.
-Disable HB functions while in rated battle grounds. (Same logic as above).
This assures your goals and philosophy behind disabling HB use in arena are met in a modern way with out hurting the real goal of the bot or what I perceive the goal as. People do not and can not solo bot current mythic content or rated bg's, so the only real loss would be the loss you seem to be okay with - users using HB's powerful API in order to automate their play in a highly competitive face to face environment.