If the Rav says they can make the bracha, then they have a source for the bracha. I personally dont know of any ashkenazim who have made a bracha at a simchat bat, but I do know several who have made a simchat bat, including the mizmorim and pizmonim, everything but the bracha.
The fact that the person mentioned by the OP made a bracha does not mean there are sinister thoughts of feminism, it could mean they are copying what they see their sefardi friends do and figure works for them too. not everything in this world is motivated by something bad.