It's not really an issue.
Even with a seriously low battery, a stationary EV hardly uses any power. It's the traction motor that uses the most juice. As long as you are not sat there blasting the heating, the emergency battery reserve will normally have way more power for heating than you really think. Youtubers regularly run these EV's until they die. There are so many warnings before they do, including reduced power modes. The heating part doesn't use that much.
So if you are travelling along and need to recharge, but you are suddenly held up, you just switch the car off, and run the heating on low. The seat heaters are another way of conserving power (heat the body, not the whole car). You would be silly to run an ICE car on fumes on the motorway, same as an EV etc.
But it is the same scenario for ICE. If they are on empty, you will still have the same problem running out of fuel.
The heating system on an EV is very efficient. On a 300 mile journey (the max my car can do on a single charge), the heating/aircon system has to run the whole time (around 5 hours) including powering the car. This is in addition to power the motors. So if you get stuck, there isn't much worry about running the heating on enough to keep warm. . There are some videos about showing a battery on around 20% can heat the car for 24 hours.