One explanation I heard that visible light lasers have too long wavelength to effectively pick up the imprinted sound. Contact patch of elliptical stylus is around 3um. Wavelength of green light is about 500um. It is hard to make optics that reads the spot with that wavelength. They likely need to get into deep UV light to make it work. Coherent light sources for wavelength below 100um are not simple or cheap. Likely need to use synchrotron particle accelerator for that.
You have your micrometers and nanometers confused. Green light is about 550 nm . Blueray lasers are about 405 nm , 100um is in the far infrared. The 780 nm laser on CD players is 0.78 um. Near IR. But still readable by a silicon room temperature photodetector which is why we have CD players.
If you think you meant 100nanometers that is in the vacuum ultraviolet and causes rapid ozone generation and if you did shine that wavelength on vinyl especially black vinyl it would have an effect similar to strong acid. It is one of the things they use to remove organic molecules as well as dust specs from silicon chips during processing.
There are near UV (395 nm ) LEDs but I don't know about Lasers shorter than 405. The fact that those are used in Blu Ray players means they are MASS produced. Although lab lasers from china have become quite reasonably priced lately. Maybe they are already popping back up. I don't follow them anymore. Edit: yes, 405 seems to still be the shortest mass produced inexpensive laser wavelength. But according to the above the ELP uses red lasers iirc. The detectors are much more sensitive at that wavelength.
The electron microscope pictures are movies made with a series of still pictures and not actually real tracking. It IS possible to make identical pictures , optically using focus stacking. This issue is not so much resolution as it is combined resolution and depth of field. But neither focus stacking nor scanning electron microscopy can image things which are moving. The image is constructed in SEM by raster scanning. There are actually some focus stacking schemes that are getting quite fast but not fast enough to image a phono stylus.
The above you tube of the ELP record player sounded pretty good to me though it was a ytv. I would love to have one of those but they cost about $18,000.