Two ports at once have been used for Samsung’s 5120x1440 240hz monitors. Each port refreshes half of the screen and there are two scanlines going from left to right. Using the calc here you might be able to use two DP2.1 UHBR80 cables with DSC and nonstandard timings to run 4k 1000hz 10bit.
This is taking a laptop CPU and stuffing it in a handheld. The laptop CPU already has the npu and removing it would require a new SKU which would cost money for special handling for packaging, new firmware, new drivers, and probably more costs I haven’t considered. You would save on the silicon but unless they have high volume, removing the npu is likely more expensive.