While it may not be extremely serious for home and HEDT uses, just a few percentage points, just imagine if you have a server farm with hundreds or thousands of drives. Remember that while the tested Haswell Xeon processor is old, servers have a very long life span due to the costs involved, both in hardware/software and in downtime, so it is very likely there are a number of these units still in operation.
https://tomshardware.com/reviews/intel-amd-storge-test-mds-zombieload-ridl-fallout,6146.html
https://www.phoronix.com/scan.php?page=news_item&px=Haswell-Xeon-Zombie-Load-Ref
