From the engineering point of view, the single opening saves the space of the elevator shaft.
But because the elevator in the hospital needs to transport the beds, the width of the beds must be considered.
For example, if the hospital bed is 0.8 meters wide, the two side by side are 1.6 meters wide, and the elevator must be at least 1.6 meters wide. If the elevator doors are opposite, the elevator shaft must be designed as 1.6+0.8+0.8. If it is single-open, since the elevator doors can be folded, the elevator shaft only needs to reserve a space of 1.6+0.8.
From the perspective of hospital infection control requirements, not only the design of elevator doors, but also other doors, requires consideration of airtight functions. The closing of the two-way opening door will easily lead to loose closing after a long time, while the one-way opening door only needs to set up an "E" type structure to ensure a tight closing.
You can carefully observe the doors inside the hospital, especially the operating room, all of which open and close in one direction. Even if a double fan is designed, only one fan can be opened and closed under normal circumstances.
Hospitals with better infection control, under the correct circumstances, should be from an elevator door to the opposite elevator door, and the elevator has its own air shower function.
The first consideration in the architectural design of hospitals should be infection control principles, followed by other factors.