In general there is in fact shield decay, however in the current config it is set to 0 per frame. So no currently there is no shield decay in the game.
We set up the rules and docs page to automatically update to handle most main-season config changes. The shield decay stuff is hidden in advanced details if decay is zero, but the bullet point you noticed is not static and will not be hidden.
I should be able update this so it is also hidden when decay is set to zero. Expect this change in the next few weeks.