I have summarized my understanding of distorted sanna as follows:
Distorted sanna refers to bahidda sanna.
It arises according to the built in system of indriya (manomaya kaya + physical body) which causes distortion.
Bahidda sanna creates the illusion that external objects possess attractive or repulsive characteristics.
However, external objects composed of apo, tejo, pathavi, and vayo are neutral.
This illusion can be overcome by understanding the mechanism that drives the system.
It is Paticca Samuppada.
Indriya samvara refers to the process of gradually eliminating ajjhatta kaya by understanding this distortion.