> The center of rapid or intense development or change. noun
> The starting point or most basic level.
The author used it correctly even though you got triggered by the word.
And I think that the meaning "most basic level" is wrong- the dictionaries might be simply recording a rare and wrong usage of the expression.
The primary semantic connection is the misuse of the phrase "from the ground up" and conflating it with "ground zero." There's no direct or indirect semantic relationship between something explosive or chaotic or destructive, and deliberately and methodically building a language model, in a calm and rational process. The meaning doesn't map to the phrase in the context of this article's title.
If you were building an etymology website from the ground up, you'd hope it would be ground zero for an explosion of awareness about how different words, phrases, and sayings could be used correctly in different contexts.
Something like that - I was trying to be considerate about the Ground Zero memorial, and the many ways in which "ground zero" can refer to things that people are deeply invested in. My personal stake is just an observation that it's not quite the right turn of phrase for the use to which it was put.
It seems likely that "from the ground up" was the intended phrase, and it might have gotten awkwardly revised, since the word startup is also in the title?