Matrix jobs that use the xUnit plugin do not show aggregate test results in the project list.
In the example picture, the Linux build is a freestyle job that builds a single configuration, runs the tests and collects results using xUnit. The same is done in the MSVC project, which is a matrix project (32/64 bit, debug/release), and the test results are shown in the project configuration's overview, but not on the matrix project's overview or in the main project list.
This looks similar to
JENKINS-12205, which has been closed since some time.