After reading the information in the SWX Help and this great information from Cati I decided to do some test with this improvement.
Both Parts I used for the test have the same history.
Create in SWX 2013.
Update with FVUT to SWX 2019 SP 3.
Test (before and after update thread) was done with SWX 2019 SP5 with a local copy of the parts.
The increase of the rebuild time about 246 % in the second part was really a shock for me.
Did anybody made the same experience?
Is it possible the increase is caused from a bad setting in my client?