I am puzzled by the SS Xhosa being classified as a 'cruiser'. The Xhosa is not a warship nor a cabin cruiser (pleasure boat). This ship is a freighter.
Based on the dedication plaque alone, I would speculate that the vessel was once a Starfleet cruiser back during the TOS/TMP era, and by the TNG era it was relegated to freight duty (like the Lantree in "Unnatural Selection"). The Norkova was definitely in use by the Federation, if not Starfleet, and its interior looked similar to TNG-era Federation and/or Starfleet vessels. The Xhosa, the interior of which looks to be from the TOS era, could have been sold by the Federation and/or Starfleet to an independent owner, no longer being a ship of the line.
The only drawback to this theory is that the ship does not look in any way like a Starfleet vessel, with the usual saucer/nacelle configuration.