I have seen this too. The reason the skull changes to fleet look is from having a Harvest mission sent to the location(as shown in your first picture) along with attack fleet. The other page still shows due to page refresh issue. when something is done on the page it would update again like hitting refresh, until then it shows pirate skull. It is server update/latency thing. Like not always showing icons with your missions on it for planets like attack, espionage etc., same thing.