That said, I'm not a native english speaker and I don't live in US - maybe it's more common than I think.

Though I have seen some small businesses working in technology refer to themselves as startups without really understanding the definition (or because they're trying to sound "sexy" to recruit developers).

Really, we've got four different terms we're trying to delineate.

"Exponential growth business" vs. "Incremental growth business".

and

"Unstable business with total expenses exceeding profits" vs. "Stable business with total expenses below profits"

All 4 permutations are valid. I personally like putting the startup vs. small business terms on the first category, which makes for the 4 pairings ["stable startup", "unstable startup", "stable small business", "unstable small business"]. I think this helps prevent the confusion that makes fruit stands think about E rounds.