When using the breadboard you didn’t connect anything to the EN (enable) pin of the driver (see the pinout and the schematic in the tutorial). This means that this pin is LOW and the driver is always enabled.
Now, there are great tools out there for the Propeller, but Parallax don’t make it particularly straightforward to find them. The ASC+ product page, which was my starting point for information about the board I’d been given to test, links only to a dry schematic ( none the less useful...
With the Step pin we control the mirosteps of the motor and with each pulse sent to this pin the motor moves one step. So that means that we don’t need any complex programming, phase sequence tables, frequency control lines and so on, because the built-in translator of the A4988 ...