I am aware of both things, and it wasn’t a misinterpretation. Although permissive licenses do directly uphold the same freedoms as copyleft ones, copyleft ones have the potential to protect those freedoms by preventing forks from messing with those freedoms. MINIX upheld FOSS definition freedoms, but Intel didn’t. Now Intel ME is everywhere and people aren’t too fond of it.
In the case of copyleft, I could say “I can trust that forks of this project won’t disrespect FOSS freedoms”. It gives assurance that someone’s contributions won’t be used by forks in a proprietary way. If I contribute to Chromium, I contribute to Chrome, Edge, and Opera, which I may not necessarily trust.
It doesn’t necessarily ensure the core project itself won’t turn proprietary if there is a CLA (okay I may be misunderstanding this part), but it can complement a good track record of FOSS committal.