I have fuzzy recall RPi5 uses 10-bit internally padded to 12-bit for output in some circumstances as the SoC doesn't natively support the required 10-bit output. There is some upstream work being done to improve output from Kodi which might indirectly influence things, but the direct and short answer to the question above is "No"
I think you are thinking of the yuv422 4kp60 hdmi output.
It's the hdmi spec that doesn't support 10-bit explicitly - it just uses the 12-bit timings with two padding bits.
Even if it did, it would look identical (there's no logical reason why sending 10-bits would look different than sending 10-valid-bits in a 12-bit word).