Actually you can do it with avs+ using dither tools, if you use the stacked format
I think Firesledge (aka Cretindesalpes) retired from avisynth stuff before avs+ became more stable (where you can use native formats now), so you can use the hacked 8bit MSB/LSB stack format (which was used for higher bit depth formats when he was active) ; I don't think dither tools was updated for the native pixel formats
Code:
LsmashVideoSource("checkers-444.mov", format="YUV444P10", stacked=true)
Dither_resize16(1920,1080, kernel="box", csp="YV16")
ConvertFromStacked(bits=10)
There are some slight histogram differences, but it's quite close. Might be some minor dithering or rounding differences