Sometimes its awkward, sometimes it is fitting.

Of course if you're developing one and you mention the PoS POC you could end up in hot water.

I had the misfortune earlier in my career of working for a total megalomaniac chair-flipper. One time he described some fairly vague product concept and I said, "ok, let me put together a proof of concept". He blew his stack and said, "no, I don't want a proof of concept I want a working product!"