Questions on some sense code definitions

[Our unconditional guarantee does not apply.]

    The sense code tables in the SCSI2 std standard indicate that the
    asc/asq 09/00 "Track Following Error" might be used by direct and
    sequential access devices.  But the following ascs/asqs would not be
    used by those devices.

        09/01 "Tracking Servo Failure"
        09/02 "Focus Servo Failure"
        09/03 "Spindle Servo Failure"

    I guess I can see why you might not get a "Focus Servo Failure" from a
    disk drive.  But why not the "Spindle Servo Failure" or "Tracking Servo
    Failure"?  If these aren't used by disks, then what sense codes would a
    disk return for spindle speed errors?

    Patty