The term "banana clip" has been around for some time now. You are correct in your presentation, but because of common usage, when the term "banana clip" is mentioned, people automatically think of the curved magazines.
Yup. Just like "assault rifle" is now used to describe any semi-automatic military-style rifle, when (as I'm sure everyone here knows) a true "assault rifle" is a selective-fire weapon chambered for an intermediate cartridge.