The Auto Buff Gem

The thing is, you don't need to add the skill to the macro in order to add it to the Auto Buff Gem. Making it dead irrelevant to the situation other than saving you a skill slot.

What they're saying isn't that you need to have the skill on a macro to put it in the auto buff gem. The point is, if you are able to macro it, you can most likely use it with auto buff gem. The only exceptions being summons and reflect skills.

It's not about macroing the skill, it's about having the ability to macro it, and a great deal of buffs that are able to be macroed can also be assigned to the auto buff gem, so it's a good indicator of whether or not you can assign the skill to auto buff, given the few exceptions.