I went on NTREGOPT website and did some reading. Apparently it does not defragment the registry, it only compacts it. I found the following note from the editor:
Note that the program does NOT change the contents of the registry in
any way, nor does it physically defrag the registry files on the drive
(as the PageDefrag program from SysInternals does). The optimization
done by NTREGOPT is simply compacting the registry hives to the
minimum size possible.
Both Auslogics Registry Defrag and Free Registry Defrag v2.35 Defrag, Compact and Optimize the registry hives. I will continue to put those two programs to the test. Auslogics Registry Defrag is updated every ragularly.