I think "startup" may be being used differently in those two context. Its fine in the US for a small business to not seek explosive growth and to have a steady, reasonable income and employ some people -- but that's not usually called a "startup" (around here, the term "lifestyle business" gets thrown around sometimes.)

"Startup" is generally used for something that is (or seeks to be) VC funded based on a vision of investors realizing immense gains in an eventual acquisition or IPO.

It sounds like its quite likely what you are calling "startup" in Germany and what is called "startup" in some US-centric contexts (like HN) are not really the same category, and that the former is broader than the latter more than what is acceptable in Germany being different.