Among the many changes, the new rules would require batteries in consumer devices like smartphones to be easily removable and replaceable. That's far from the case today...
The Galaxy S5 from almost a decade ago had little issues with waterproofing IIRC, and it had a replaceable battery
I'm pretty confident the manufacturers can hit the ground running with a sleek waterproof device with a replaceable battery - they can even do what LG did and make the battery slide out the bottom, if they want to keep a solid glass back.
I wonder if the ability to easily unscrew a backplate with regular screws (like PH00) and replace the battery underneath would still be enough for the regulation.
Jack and charger ports can be controlled by the phone to turn off if there is low resistance (ie water) between contacts.
A battery is harder, as it's what provides the power to the thing that decides whether to turn off the port. Not that it's impossible to put some smarts into a battery, to decide when to power the output. But it's going to add a lot of complexity and bulk to do it (switching circuit, logic circuits, etc)
Gigaset GX are MIL-STD-810H and IP68, quite a lot more than the Fairphone which isn't rugged as such. I don't think Gigaset even produces phones without replaceable battery.
A small o-ring and something to clamp the battery/battery case down would be more than enough to make these phones as water resistant as current phones. If they lose water resistance, it's because the company's trying to be shitty