....
But I don't know where you got the conclusion that "hi-res" LDAC @330kbps is worse than SBC only above 18k. It actually has worse noise right around 10k, which most people can hear all the way into old age, and then it has something that looks like extra harmonic distortion around 13-14k as well. SBC measurement for comparison:
https://www.soundguys.com/wp-content/uploads/2018/10/SBC-Bluetooth-Noise.jpg
Of course, as we know from NwAvGuy and other sources, problems below -85 dB are not audible in the vast majority of real-world listening scenarios, and as such most of what we're seeing on these graphs, even stuff above the "16-bit (no dither)" threshold, is not going to be audible. But even while acknowledging this, the "hi-res" 330kbps LDAC setting still comes out poorly, with that 10k noise rising up as far as -75 dB and becoming possibly audible in very good listening environments (which doesn't happen for SBC anywhere on the spectrum).