This is different because Firefox Focus, a separate app, only blocks ads while using Firefox Focus. Firefox Focus can also be set as a Safari Content Blocker which allows Safari to benefit from Firefox Focus's ad blocking. (It's not the best ad blocker, I've found wBlock - https://github.com/0xCUB3/wBlock - is more effective, anecdotally and via adblock.turtlecute.org)

Regular Firefox (non-Focus, the app from the article) can not benefit from Safari Content Blockers, and therefore does not benefit from Firefox Focus's ad blocking.

I think gp means the other way: Firefox can not use Safari's content blockers to benefit from them.

thank you everyone for your time and insights, especially those that challenged me and opened me up to new possibility.