Different technologies and a marketing consequence as existing led TVs aren't really led.
Originally we had LCD TVs and they used a CCFL backlight and were bulky. Eventually manufacturers switched to using LED backlighting to light up the LCD pixels in front of it. For reason unknown these are referred to as LED TVs which they arent.
These Led backlit LCD TVs are available at 8k. However the led backlighting is still quite large and typically only has up to 500 LEDs lighting up the LCD grid.
Microled in the other hand does away with the LCD grid as each led is a sub pixel in its own right and like oled generates the light itself. However with these micro LEDs they are still much larger than the LCD so even at 110in they can only pack in enough to achieve 4k resolution.
They would need to reduce the size of each microled down to 1/4 to get a 55in microled screen and down to a 1/16th to achieve an 8k 55in microled screen.
Going to be a while before that happens. In the interim we have mini led which reduces the current backlight led size down to 1/40th. In theory that 500 led backlit TV could now have 20000 meaning more backlight control over individual areas of the screen. In reality it looks like mfrs are going with much less in the 700-2500 range.
Those do look great but I take issue with a number of things, if you can afford to buy that then you can afford to have a dedicated HT room AND another room with a microLED display.
I don’t understand why they feel the need to make them multipurpose rooms, normal people do that because they can’t afford or don’t want to give up a room for a home theatre so easily.
It makes no sense having amazing contrast in a room filled with light because you won’t appreciate it fully as the eye has a limited range it can see at any one time, completely dependant on lighting conditions. Not only that but having a lit up room detracts from the focal point of the screen when you can see other things.
Granted it can do HDR far brighter than a projector, although at that screen size I’d argue it’s too bright, however I’d personally money not object get a Christie Eclipse projector and an acoustically transparent screen so you can have the audio coming from behind the screen rather than the ceiling or floor like you’d have to with a full wall microLED which is a big audio compromise and for any Atmos lovers rules it out.