There is a potential for that, but in fact the advice given in Australia by road safety advocates like me is that everyone who is pulled over by the police and comes in contact with them during a traffic stop should be breath tested, whether that's for speeding or distracted driving of any sort. That practice does vary a little from state to state, and once again, it depends on the workload of the police.
Overall, the key aim is to create the impression of drivers that whenever they come into contact with the police, there is a high likelihood that they will be breath tested, and in doing so, really create that deterring threat. The point I'd really like to stress about random breath testing is that, although it catches drunk drivers, its key goal is to deter drunk drivers. What's more important is the threat of being breath tested, rather than everyone always being breath tested.