That only works for the Bounty mini-Map Arrows.
It does not work for Visions Portals. However, if you mouse-over a yellow Arrow and a label does not pop up, it’s a good indication that it is a Visions Portal.
On the Area Map you can get the same result by mousing-over the pulsating Bounty circle. And, a Visions Portal icon is shown instead of an Arrow or circle.
