True, the above comparison might not have been the most scientific :P The Spring 2018 results were run on a much more powerful desktop than the surface pro 3 used for the insider results.

Here is the results for the April 2018 Update rerun on the same surface for a more apples to apples comparison:

    C:\tmp>.\ProcessCreatetests.exe
    Main process pid is 6448.
    Testing with 1000 descendant processes.
    Process creation took 4.382 s (4.382 ms per process).
    Lock blocked for 0.007 s total, maximum was 0.000 s.
    Average block time was 0.000 s.

    Process termination starts now.
    Process destruction took 0.592 s (0.592 ms per process).
    Lock blocked for 0.002 s total, maximum was 0.002 s.
    Average block time was 0.000 s.

    Elapsed uptime is 0.01 days.
    Awake uptime is 0.01 days.

    C:\tmp>.\ProcessCreatetests.exe -user32
    Main process pid is 11364.
    Testing with 1000 descendant processes with user32.dll loaded.
    Process creation took 4.707 s (4.707 ms per process).
    Lock blocked for 0.009 s total, maximum was 0.000 s.
    Average block time was 0.000 s.

    Process termination starts now.
    Process destruction took 1.248 s (1.248 ms per process).
    Lock blocked for 0.904 s total, maximum was 0.902 s.
    Average block time was 0.181 s.

    Elapsed uptime is 0.01 days.
    Awake uptime is 0.01 days.

The mouse movement hanging behaviour is easily evident with the April 2018 release. I didn't notice the same on the insider build.