The PCROLL functionality is not intended to hide things from the players, but to allow them to roll their own saving throws. The traits are included so that any conditional effects can be properly processed (e.g. SAVE: 1 item, poison).
In the example from @Oladahn, we're specifically talking about the name of an unidentified NPC showing in the label of an effect. This is different from players seeing disease, poison, etc. effects. If you want to hide effects from players like you mention, change the effect to GM only.
On a side note - I'm implementing a "SCRT" button (secret) in the modifier buttons on the desktop - this will have the effect of making a check secret. I hadn't considered expanding this to make effects GM only when they're applied with the SCRT button enabled, I'll consider this while doing the development.

