Question – Why is this HDD so slow?

WD Green HDDs have a rep for being slow, but I would like to understand why (at least by looking at the specs); this drive isn’t much slower than I expect for a WD Green of its age.

Take for example this drive: WD15EARS.
Trying to find some decent (and hopefully accurate) specs is tricky, for example this site:

WD15EARS Western Digital 3.5″ hard drive with a storage capacity of 1.5TB and featuring a SATA interface. WD15EARS-60MVWB0 Western Digital Caviar Green 1.5TB 5400RPM SATA 3Gb/s 64MB Cache 3.5-Inch Hard Drive. All information about the Western Digital WD15EARS hard disk drive: technical…

hddfaqs.com

I suspect is either AI-fuelled or maybe a bunch of data lazily slurped from different sources because the “failure symptoms” information is either very generic or so generic that it’s as good as junk.

The SMART data looks fine, but the write performance of the drive is as poor as I would expect from a WD Green 3.5″ drive, so in this case a 1.5TB drive that is probably averaging about 45MB/sec write performance (I saw it peaking at about 65MB/sec so logically it has a USB3 link) via USB3 for large enough files to get its teeth into. If I picked a random 2.5″ old 500GB/1TB drive from my collection, I’d expect to write ~100MB/sec via USB3.

Any ideas?