To be disassembled into parts for the upgrade are not the two nuclear-powered land cruisers, but rather the prototype not polluted by nuclear radiation.
In fact, this is also inevitable. Although system upgrades can deal with nuclear radiation, the system will not regard an integral thing as parts. It must be disassembled first.
Disassembling those two nuclear-powered land cruisers would inevitably lead to a large amount of internal nuclear radiation leakage, so they can't be disassembled.
Since the nuclear-powered ones can't be disassembled, naturally the prototype with no radiation has to be disassembled.
Although the 305mm twin turret, as the main part, couldn't be disassembled without a large gantry crane, there are still small lifting devices in this base that can take apart other parts.
After a round of disassembly, what remains of the prototype is just the internal main structural frame and the 305mm twin turret that couldn't be disassembled.
