Initially, LoROM was designed to be compatible with the NES, with the idea of running NES ROMs directly on the SNES (although it was not perfectly realized in the end; the 6502 part was perfectly compatible, but the APU and PPU needed to be emulated). HiROM, on the other hand, is a completely new SNES cartridge design specification. The actual running speed of both is not much different; it's just that LoROM uses a 32K mirrored symmetric space.
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Nintendo built two sets of memory controller pin mappings for LoROM/HiROM. In fact, it's completely unnecessary to make it so complicated. On the cartridge side, compatibility can be achieved simply by swapping ROM address lines.
Therefore, we only need to use a pinswap program tool, and there is no need to design two separate PCBs (any LoROM or HiROM that we may just only choose one).