The quote you copied say no performance but you forgot the note below it “With the exception of Thunderbolt, eSATA and USB 3.0 external hard drives” because the WD Elements I have is USB 3.0 and connected to USB 3.0 port so yes cache have performances effect.
Plus whenever it is only USB 2.0 it could still have some performance effect when there are a lot of head activity (seek-time) if this activity make the hard drive slower than USB 2.0 max speed (if re-read data are still in cache that mean less seek-time loss).
And the reason why I am asking all this is because this hard drive provide strange benchmarks result compared to all other mechanical non-Hybrid hard drives I have (internal or external).
For example it can provide a stable reading curve all over the disk surface that “should” not be possible with mechanical hard drives because the closer you go to inner side of the disk surface the less data you read per rotation, this HDD also provide very good results (ten times higher than usual) on CrystalDiskMark with 4K block write test.
So I am trying to find an explanation and figure out how this is possible or if this drive fools the benchmark tools (and id it does … how ?).
Hope my english is not too bad, I am not english native.