You will not suffocate with the climate control on recirculate. To add to what others have tried to illustrate, there are many leaky areas where air exchanges between inside and outside, some by design, and some by accident. There are loose seals around doors, there are gaps around wire and hose entry points, there are gaps around the door handles, the list just goes on and on. If you have Recirc on and just HEAT, then you will definitely get a buildup of humidity which will either fog or frost your windows, and this is more extreme with the car stationary than if the car is driving. But, the illustrative point of this would be to drop a car whose windows and doors are closed and the HVAC is on RECIRC into a body of water and watch how quickly and completely the cabin fills with water. It will be pretty quickly and evenly filled to the roof as the car sinks to the bottom of the body of water.
I'd guess that Tesla and most other car manufacturers have used the "LOWEST COMMON DENOMINATOR" (you have to protect against unwary people doing things that will get them killed) approach in designing systems that don't allow non-savvy people to kill themselves in their parked cars.