There is no "street legal" statute, so it would have to be for something specific like an improperly displayed license plate, that one example in the article alludes to.

But other examples in the article like "Often officers simply wanted photographs." would not be a legal reason.

Now, in practice, this is a very easy standard to meet, because even if an officer wants to pull someone over arbitrarily, they can simply follow someone until they make a very minor infraction like crossing a line improperly, exceeding the speed limit by 1mph, rolling a stop, or failing to signal... but they still have to do it.