Why am I using YCSB for testing mongo4.4 and 4.3, where the effect of 4.4 is lower than 4.3

I used YCSB0.17 to test the data of versions 3.4 and 4.4 of Mongo, and found that the performance of version 3.4 is superior to that of version 4.4. Why is this. The configuration of Mongo and the pressure testing configuration of YCSB are both the same, using the same specifications of server configuration information. I found that others tested data 3.4, which is also ahead of 4.4