On the Java Application page, the selection forwarding from the threads table to the Properties/Stacktrace view is tricky to understand, since it involves the selection (not the checked state) of the chart legend.
This is to make only one type of items is forwarded to the Stacktrace view, so the user won't see profiling and allocation information mixed together in aggregated stacktraces. This selection comes from the getDefaultSelection method.

However, it is quite confusing, especially since the selection can be on an element that is not part of the "thread related" items, and the selection will then be empty, and that the selection can be on a legend item that is not checked.
To fix JMC-5043, if the checked state is only one legend item, the "default selection" calculation is skipped, which fixes that bug and make the behavior better, but probably harder to understand...