The fact that Hakkenden is published on a BL magazine doesn't mean it is actually BL.

I agree. Admittedly, I haven't read past the point at which Bliss stopped releasing, but there isn't the slightest hint of shounen-ai in the first 3 volumes, save for some of the silly dude-looks-like-a-girl jokes you find in every other manga.
And this was originally serialised in a shoujo BL magazine (which means the stories were mostly shoujo with only the slightest traces of pre-slash); it got switched to Ciel Tres Tres because Ichiraci now publishes only shoujo romances and probably think that serialising something written by a shounen-ai mangaka is damaging to their image or something.

No more BL than Kuroshitsuji or Fushigi Yuugi.
Just the normal slashiness and jokes. Enough to be interesting, without being offensive to the general public.

Slashy, yes. BL, no. It's much like Silver Diamond (anyone who thinks SD is a yaoi has been sadly deceived).

I like it if it is BL ! I will buy if it is BL 🤣