Thanks for your message and the information.
No, I can confirm that generally Hard Disk Sentinel DOS (HDSDOS) detects the capabilities of the SATA controller correctly, just like for the connected hard disk drives / SSDs.
The controller may be SATA 3, but currently with this hard disk, working in SATA 2 mode.
This is not surprising as this hard disk is a SATA II hard disk: as you can see in the Serial ATA Features section,
S-ATA Gen3 Signaling Speed (6 Gps) = Not supported.
This is why the AHCI negotiated speed is 300 MB/sec, as appears in the Hard Disk Summary.
The official manual of the hard disk also confirms that this is a SATA II hard disk ( ... up to 300 Mbytes per second, see http://www.seagate.com/staticfiles/support/disc/manuals/desktop/Barracuda%207200.11/100507013c.pdf
Personally I see no problems or troubles, both the hard disk and the controller and the negotiated speed is detected completely correctly.