Glad to see you did your research! While AR 670-1 does specifically state it is your choice, there is an ALARACT message that may be the source of confusion. Please see the file I’ve attached to the bottom of this post.
Let’s say you are absolutely 100% correct. Are you sure you want to become the martyr for this issue within your Brigade? This may be one of those issues where it is smart to pick your battles. It appears your command is not going to be receptive to a change. I would encourage you not to fight this battle as the last stand, as I do not see any benefit to it. Sometimes in the service it is just better to shut up and color.
Now with that said there is absolutely nothing wrong with trying to understand the basis for a decision. Usually command teams don’t just make things up because they want to. In this case perhaps they are following other guidance. There is a chance that the command team just decided that’s what they wanted for uniformity and morale purposes. Typically in these situations the command will issue a uniform supplement to AR 670-1 and then unit personnel are required to follow it. Usually these supplements are in writing.
Trust me, I like to know the why’s of things–especially when I disagree with them… but it is not always the smart move when you have a career to consider. Pick your battles and win the battles you pick.