You still haven't learned to make your case, have you?
First of all, you have strayed far away from the article under discussion and have gone back to your zero-tolerance mode; we have two glaring examples here in this story that are unaddressed by the writer and the greater number of posts here:
1)We have a situation where officers are drinking on duty, albeit in small amounts, and then, themselves, driving in pursuit of their secondary purpose, which is the witnessing of a crime in progress. The undercover officers are assumed to be there to provide critical testimony in court as to the defendant's actions prior to and subsequent to the arrest.
2)Only certain patrons are targeted, the most obviously impaired or the heaviest drinkers where impairment isn't obvious, and then once having left the bar and entering upon public property are allowed to commit the lesser crime of public intoxication long enough to get in their cars, drive onto the highways and then be pulled over by accomplices of this ruse for purposes of escalating the nature and degree of the offense.
Now, both of these important deviations above from the normal and usual duties and responsibilities of a patrol officer are not likely covered in any performance standard that you are likely to be privy to read.
Other than these little details, I think drunk drivers ought to be nailed as you do; I think we have better things to do than to fabricate the conditions to increase the catch just because the fishing's been slow lately, though.