The offer is very seductive but the pen behaves weirdly. I tried it out in store and when you place the pen on the screen it does not react as a touch. You need to press it harder for it to start working. As opposed to apple pencil it starts drawing as soon as you hit the glass. And even on wacom tablets as soon as you hit the plastic of a tablet it works. On S9 which is supposed to be a flagship model it feels like the pen lacks responsiveness at light pressure levels. Is it a bug or does anyone share my insights ?
What you are describing is most likely due to the alarm used at that store. The magnets of some retail alarm systems mess up the s pen tracking.
When used away from those magnets, you will see that is registers even before you touch the glass.