Selector stops have no real use for a semi auto receiver. For an M16 receiver with a factory M16 selector, without the stops, there would be nothing to prevent the selectors from over-rotating. Battle Arms M16 selectors do not require selector stops, as the center has been redesigned to not over-rotate regardless of the stops' presence.
On a semi auto receiver, the selector center itself is responsible for limiting its rotation.
One of the three changes Battle Arms specified and recommended was the removal of the stops, because they are unnecessary and therefore useless, and the forward stop is very close to the SAFE engraving, making it look somewhat busy.
Their presence just means more machining on a billet receiver. The recommendations put forth by Battle Arms are just that, recommendations. In the end, if it looks good, then everyone is happy.