That rating comes in handy for those who have butter fingers like me and drop their phones in water once in a while.
If it was possible then it's possible now.
The comment I made doesn't require that I push, or be for against, some higher narrative that you seem to see me as having in my head. It's perfectly valid to criticize the technical merits of an individual comment. If you see that as weaselly, then tribalism has infected your mind.
Does it work? Well, one of the phones used to be my daughter's. She forgot to take it out of her pocket when she put her trousers in the washing machine so it ended up going through a full wash and spin cycle. It still worked, there was no water ingress in the phone itself. The earpiece did seem to have gotten damaged so I replaced it (5 new earpieces for $2.50 incl. shipping, I still have 4 left...). This phone is now used as a media player, running mpd which can be remotely controlled from other phones in the network. It connects to my jobsite radio (an oversized and overweight boombox I made around an old car MP3/CD/Radio with 2x40W speakers with bass reflex and a SLA starting helper/power pack) using that 3.5mm jack.
Couldn't the jack itself be made to be water resistant? Seal it up and use relatively inert metals for the contacts.
https://www.gsmarena.com/sony_xperia_1_iii-10712.php https://www.gsmarena.com/samsung_galaxy_s10-9536.php
a lot of their phones still have headphone jacks as far as i know. seems like they are the only decent company left in that regard