Maybe the motherboard is made because the 68000 is 16 bit and a 68030 is 32 bit ?!
If it's using the original (O|E)CS chips then presumably only the local 030 fast RAM will be 32-bit and the path into the chipset 16-bit. In that respect, no different to an accelerator.
However, that's an assumption. I don't know that they aren't going to use some FPGA solution or other, but there sure are a lot of sockets on the board.