Not true. Fill rate and memory speed is still a huge bottleneck. The issue is not “rubbish” but memory speed. It is almost always memory speed, cache, ram, disk etc.
There is this misconception that if one uses js or c# to tell a gpu what to do it is somehow slower than rust. It only is if you crunching data but moving memory to the gpu and telling gpu to crunch is virtually identical.
PCIe 6.0 x16 delivers ~128 GB/s so the billion points can be loaded in milliseconds onto the GPU. The GPU's memory is much faster.