IIRC, a screen readout during one of Voyager
's Borg-related episodes showed that thingy to have been
a multikinetic-neutronic-mine-or-whatever. Presumably Lore found one, took it over and retrofitted it into a starship; this does not seem entirely out of character.
A VGR episode may have reused a shot of that miniature and labeled it as something different, but that doesn't mean you should take that reuse literally, any more than you should with any of the hundreds of other reuses of ship miniatures, FX shots, makeup designs, actors, costumes, etc. The idea of converting a mine into a starship makes no sense. A mine is a small thing that blows up. You can't retrofit a hand grenade into a truck.