The Martin Mars is
not amphibious - it cannot
land on or
take off from anything but water, and had no integral landing gear.
It could have motorized "beaching gear" bolted on temporarily once on the surface, to crawl out of the water onto a ramp, for maintenance or other needs. As did its sibling, the PBM Mariner:
https://www.beamng.com/images/import...3c62e32eb0.png
So "largest amphibious aircraft" is correct with regard to the AG600, which
has integral retractable landing gear for solid runway operations.