What conflicts will a aw15r3 motherboard cause installed in a aw17r4

I have an AW17R4. I am told the motherboard needs replaced. The tech installed the new motherboard. He said it was smaller than the original. He then brought up the BIOS and it said it was a AW15R3. I made him remove it and put the original back in. I know that a mother board set up for an  AW15R3 would cause all kinds of conflicts with the drivers, registry and all related software in the AW17R4. I am being told by the supplier that it won't make a difference at all since they are the same part number.

Any answers, advice, experience, anything will be greatly appreciated.

Thank You