slimportconnect.com says:
What display resolutions does SlimPort support?
SlimPort supports display resolutions up to 4K Ultra-HD. This includes Video Electronics Standards Association (VESA®) digital monitor standards up to 4160 x 2160, Consumer Electronics Association (CEA)-861 display standards up to 3980 x 2160, and everything below. When a mobile device is connected to the display, the device will automatically output the optimum resolution of that display; it is a true plug-and-play solution.
I will try to test a low-res display myself today...
If true that would be an Android restriction.
slimportconnect.com says:
What display resolutions does SlimPort support?
SlimPort supports display resolutions up to 4K Ultra-HD. This includes Video Electronics Standards Association (VESA®) digital monitor standards up to 4160 x 2160, Consumer Electronics Association (CEA)-861 display standards up to 3980 x 2160, and everything below. When a mobile device is connected to the display, the device will automatically output the optimum resolution of that display; it is a true plug-and-play solution.
I will try to test a low-res display myself today...