So what the heck has happened with LK-99 really?

For example, all metal conductors in chips are isotropic, mean, conduct current equally in vertical or in horizontal directions.

Imagine, conductor become anisotropic, for example magnitudes more conductive horizontal than vertical (to be strict, usually this mean, crystal material, which have crystal axis and some properties aligned with axis).

In this case we have to make some bridges between horizontal and vertical parts of conducting path, and make horizontal and vertical parts by two separate tech process steps (really will be third step for bridge), so for vertical part, material will be oriented to best conduct vertical, and for horizontal part, to best conduct horizontal.

So automatically, conductors will have 3x tech process steps if compare with isotropic materials.

And I consider, we have automatically got some bridge material (and tech process), but this could be additional hassle (big, expensive R&D).

In reality, frequently, crystal materials grow "automatically" aligned to base substrate (most semiconductor chips based on mono-crystal), so to change conductor crystal axis orientation, need some additional trick (so fourth step), etc,etc.

All these considerations very similar to using special isotopes in chips, which already today claimed base crystal will ~50% better heat conductor, so automatically will got significant grow of working frequency, but in real production tests nothing special achieved, just much grown expenses.