Two things may be allowing you to preserve an image on TX.
The first is using a Blix. I have warned before that a film Blix is too weak to remove all of the silver. This may just be an illustration of my warning.
The second is that the TX400 may contain a lot of Silver Halide with very high Iodide, and this retards bleaching and fixing.
There are no color formers in TX400.