The very nature of poly allows for a craptastic amount of micro labelling. I for one love the terms lovers, girlfriends, boyfriend etc. They suit me.
Life partners, sisters, brothers... magick love friends etc... all drive me nuts. They don't suit me, my personality or my life.
Labelling is something that comes up for a lot of people. Especially considering some labels can denote ownership. I wish you the best of luck on finding something that suits you and your "friends"
except this kind of thing seems to matter to other people quite a bit
If I were monogamous, and met someone who didn't tell me they weren't and they wanted a relationship. I would be pissed. So I can understand why they want to know.
For the record, I am non-monogamist/open first. Poly second. I find explaining I am in an open relationship far better suits me than poly. Poly does carry a lot of.. extra stuff to it, that I don't identify with. This whole non-monogamist thing for me is like dating. I enjoyed it when I was available, the dating aspect was fun, but I am not going to fall in love with everyone I meet. Poly creates that assumption and pressure, so I do understand