The Seagate 2.5" hdds were a huge performance increase over standard hdds for loading/os booting, but much slower than their 3.5" desktop counterparts, even the 5400rpm, for sustained writing.
They were great for laptops as a compromise. Or for retrofitting a ps3 console , because a large chunk of the most common files fit on the small bit of ssd on the hybrid.
I'll maintain the position that sshds aren't useful in desktops because it's cheaper to get a small boot ssd and a large hdd, and you have the installation room for it.
Sshds are so 3 years ago. Anyone releasing an sshd now is behind the times, and they've missed the boat. It's just a "me too" product.
With SSD prices plummeting, and capacities increasing, it's now feasible to miss the sshds altogether, and just go to a cheap 256GB ssd.
With the speeds of even the the most basic ssds exceeding 300MB/s, sshds really do not have a tenable position anymore.