Swat skin already have the ability to "hide" from a distance from players, you will only be seen If you get close to the criminals
As you said, just from a distance. Once you get close blip is visible. The idea of implementing it, is to allow covert ops and surprise approach to disorient numerous criminal groups/quads. For instance, for Helis getting closer and not get shot midway, or to ambush MWs.
The idea is to allow cops to use at will those devices. With a proper cooldown between uses as in decoys