We have skipped test cases in JUnit XML file, for example: 

<testcase name="570521512 - Check specific Linux case" time="1">
   <skipped message="Test should be launched on Linux platform only" />
</testcase>

Such testcase is properly handled by JUnit plugin, and properly rendered in old Jenkins UI (non BlueOcean).

In BlueOcean results however such test cannot be expanded to see why case is skipped.

Note, that if you have <system-out> XML node inside skipped test, then it is displayed normally in BlueOcean, however skipped message is still not available.