The people that are scared of using a hairdryer on their iPhone, won't be willing to disassemble it either.
We have got to stop coddling people. We don't need to compromise on everything just so it's fully maintainable and accessible by the lowest common denominator. This law is being designed for a group that frankly does not care either way, but makes the devices worse for them in a practical, day-to-day sense.
It is hard to tell what the EU is actually looking for when you compare against the meter stick of reality.
Even ignoring potential design impacts from transitioning from sealed batteries to ones padded with safety features to avoid harm to someone armed with a conductive screwdriver, I have to imagine there will be quite a few people who do not restore the device to its ip 68 rating.
So you risk people stockpiling batteries in case they need them later, and people who after repair increase the risk of them turning their phone into a pile of e-waste because they thought they could still get it wet. People also won't necessarily know the proper way to dispose of the old battery.
This compared to just having rules about needing to supply batteries which are replaceable by any appropriate state-licensed technician at cost for X number of years, and mandating the old batteries be properly recycled by said technicians.
Starting a fire with a hair dryer, without disassemblibg it, seems almost like a challenge. What are you going to ignite with 80-90°C warm, rapidly cooling air?