Hi Macquatic,
you are so right about common names! They are so confusing.
The "butterfly" plecs I saw looked very like fat sting-rays and although they were about 4" long when I saw them, I was informed that they can grow to several feet long! So obviously they are not "hillstream loach" either, but something else entirely.
They were fresh water fish, suitable for out-door ponds and buyers were being discouraged from buying them for tanks (even large tanks). The one thing that my LFS drives me mad about is not using Latin names for things!
I'll see if I can identify my "butterfly plecs" for you, FYI.