Missing the point much?
"Brodie Clark ... said: “There was no breach of security or immigration control. E-Gates are used in conjunction with manual checking by border officials ... , and the border was not compromised as a result of the incident. The gates have now re-opened and we will continue to monitor their performance to ensure they operate safely and securely. To date more than 3 million people have used the E-Gates system.""
This is a willful smokescreen that misses the importance of this failure. The staff noticed that these two had switched passports and got through (any bets that it was a couple of teenagers just seeing what would happen, and being really obvious about it?). However, that shows that it is possible to game the system, and that there has been an unknown number of false positives generated by the system, which may only be the two in this case, but with a sample of 3 million is likely to be higher.
OK, false positives are always going to be a problem with any workable identity system dealing with thousands of people a day (as someone else said above, I know someone that has gone through borders with the IDs of several different people). The only advantage I can see here is that there is a second level of security - the staff - that aren't there when there are human passport checkers. However, they are around to deal with negatives not positives.
This is a waste of time and money, and Brodie Clark clearly knows it.