That’s not true anymore. B737 New Gen (700, 800, 900, Max) have gull wing emergency exits. They are hinged at the top and electrically deactvated when in flight.
Main cabin and aft doors are still plug type.
My understanding is this was not an emergency exit, rather a fuselage section that has structure for an emergency exit but is not used as an exit.
I’m a couple of years removed from the industry but am type rated in the B737 and had initial instruction in the MAX before they were in active service.
EC
https://www.youtube.com/watch?v=maLBGFYl9_o DOOR PLUG INFORMATION
There was some confusion during early reporting about what fell off the aircraft. It was door plug that is secured with 4 bolts. It is not suppose to "open" unless the bolts are removed. The plane can also have a deactivated door. Most of the hardware for the door is there, but is missing a few parts that make it usable. This option would be if the airline company thinks the seating for the plane is going to be reconfigured and requires the use of that exit.
It has been a while since I flew but, going through recurrent training for 28 years, every single Boeing I flew on had the overwind emergency exit doors that popped out without hinges. The forward and aft doors had hinges and were connected to the planes. I am confused how a ‘plug’ door would even work with an evac slide. They all ‘plug’ the aircraft but I am thinking they meant ‘plug’ as in like a cork, one that can be removed.