Let's look at the situation of an ST-225 connected to your 'type 1 only' board. The ST-225 (a type 2 drive) is expecting to have WPC activated from cylinders 300 to 615. The board (believing it has a type 1 drive attached) will turn on the ST-225's WPC from cylinder 128 onwards.
Thus between cylinders 128 and 300, the ST-225 will have its WPC activated when it should not. I would thus expect some read/write errors in those cylinders, probably in the cylinder range of 128 to 200, with more errors appearing the closer the heads are to cylinder 128.
How often would the errors occur? I don't know. It might only be one error per one thousand read/writes.