Questions related to Round 19 : Vibhishana should be posted here.

The example for the number placement combo has a wrong iteration of the bottom right grid.

This is the fixed version that will go in the printed IBs - https://tinyurl.com/3puaa7mh

We will release a new IB version in a day or so that's consistent with the print version. Just waiting in case there are more changes.

In the Loops bottom left grid, the shaded cell should contain a 6, and not a 5 ;-)

I believe that the top right grid of the shading example is non unique (you can either take the given solution and add a shaded cell on R3C3 or have a more snake-y solution that includes R1C4 shaded)

Thanks for pointing this out. We will update this in the final iteration.

Thanks for pointint this out. We will fix this in the final iteration.

Is the traitor rule necessarily wrong, or it is simply ignored?

The traitor rule has to be wrong at least once in the grid, but not necessarily for all instances where the rule applies.
For example in the loop section, for the top right puzzle where rule # 2: "Loop turns at black circle and goes straight through white" is broken, the loop turns in two of the white circle but goes straight through one of the white circles.