Yes, that is true, which is why wording is important. However, this article is not talking about a single post being taken out of context, it is about a systematic online persona that is affecting real life.
Except context is completely different online than in-person. Heck, online context is different for people using different devices and browsers.
In-person communication is rife with unspoken, yet understood, shared knowledge: body language, facial expressions, tone of voice, information about social standing between two individuals, etc.
Whereas we're still sorting out how to properly interact online, having only been doing it (at scale) for ~20 years.
This is probably pretty good advice for most, but I'm one of those with a dry, sarcastic, sense of humor, and that doesn't always translate well online (unless, perhaps, as a video).