"So, positive contribution margin should imply they covered all the fixed and variable costs, the way I read it."
That's not what the passage you included says. It says it only covers variable costs.
That's not what the passage you included says. It says it only covers variable costs.
So, the passage explains what contribution margin is, but TC is talking about being "contribution margin positive". How would you understand the second term?
I've only ever heard contribution used in the sense of COGS, not foxed costs.
TC has a terrible reputation for using business terms that aren't really generally considered business terms.