I don't really see the reason to compare 18 MP on DSLR to 80 MP on MFD. State of the art in DSLRs is 36-50 MP for low ISO shooting.
Regarding short sync times, it is clearly an advantage of leaf shutter technology over focal plane shutter. It is important for some kinds of shooting, but for a lot of shooting it is not very important. Just to make a counter argument, no MFD offers contrast detect AF in live view or 10 FPS per second or dozens of AF points. Being able to do accurate focus over a large part of the image area also plays a role. Horses for the courses…
What is pretty obvious today, with all MFD makers except Leica having CMOS sensors developed by Sony, is that MFD sensors are on the same development curve as smaller formats. That means that they can fully play the format advantage, just like in film days. Digital sensors are incredibly good, so making best use of them is more critical than ever. Just as an example, a digital sensor is flat. Film always had some curvature except on some Contax cameras with a vacuum plate.
So, MFD will give a significant resolution advantage, but only in a single plane of focus. So, technical cameras make a lot of sense as they can achieve extended focus for a single plane without stopping down, utilising the Scheimpflug principle.
MFD will also have something like 1.5 stop in ISO speed advantage. An IQ-3-100MP will have the same noise at 4500 ISO as a Sony A7rII/Nikon D810/Canon 5DsR at 1600 ISO. MFD being a high ISO champ? Yes, with recent CMOS sensors.
On the other hand, if you need to stop down for DoF the playing field will be much more level. With MFD you need to stop down 1.5 stop more for same DoF. That will eat up the ISO advantage and also the resolution advantage as diffraction will take it's toll (*).
Getting back to flash sync speeds, that has always been an advantage of leaf shutters. There is no reason that we have FP shutters with 24x36mm, except economics and fast shutter times being a sales argument. But, market did not ask for leaf shutters in 24x36.
(*) For most aspects, exposure time and diameter of the aperture decides the image quality. Say that you shoot f/9.1 on an 80 mm lens and f/5.6 on a 50 mm lens. Aperture diameter in both cases is around 8.8 mm, so resolution and diffraction will be the same when printed at the same size, excellent lenses assumed.