The "Hide from list" functionality is not a restriction its a usability feature.
We do not attempt to restrict information and it will still show in many places in SAP.
It's only intended for having smaller choose from lists in the system (usability).
Also note: We are not able to hide the items in the "Auto search dropdown" as SAP does not have any SDK for doing so.
In general we do not recommend trying to build a data ownership system with B1UP. Many people have tried to do this (using macro and IPT) but it is our belief that a true data ownership system needs to be part of the core product.