Yes. And if you're pulled over for speeding way up, I have never heard of a traffic cop who will ticket you.
Some online study aids for passing start with "increase your speed so you may finish the pass quickly" and end with "maintain a safe passing speed until you have created sufficient distance to resume a safe cruising speed." Others recommend a full 10mph speed difference to keep the passing time short.
I've known people to get a ticket in this exact scenario. Speeding is not allowed just to pass and will often times get you hit with a reckless driving charge, as well. Especially so if you go 10+ over the limit.
Now, if you mean someone that went less than 5 over the limit, I'm back in agreement with you. But, that is within the realm of speed that probably won't get you pulled over even when not passing?
I think the whole thing is quite subjective and certainly in part the subjection would depend on that particular officer's mood on that particular time on that particular day at that particular place.
The subjective assessment would be along the lines of differentiating between "driver slowly and casually accelerated to 10 mph over the limit, passed the car with a wide berth, and merged back with a large buffer" versus "driver suddenly accelerated from 10 mph below the speed limit to 3 above, spitefully passed closely to another car before dangerously cutting 2 feet in front of them"
I think most officers have been driving long enough to tell if someone is driving like a dick or cruising at 10 mph over and being chill. The latter will still get you a ticket, sure, but the likelihood of getting excoriated by them is less than say, 5 mph over the limit and you're tailgating and cutting people off. Some of those things maybe the cop can't legally write you up for, but the cop will see, can tell, and will make sure that you'll get written up for some thing or another. And hey that's a good thing, nobody likes a douchey driver.
If you casually and slowly accelerated to 10 over, passed with a large berth, and then presumably dropped back to speed; this was not a rapidly executed pass and I question if you should have even done it?
You are right that they have discretion. So, yeah, it is subjective. People online get way too defensive of aggressive driving. Seemingly without realizing they are describing aggressive behavior. And if you are at all worried you will have to exceed the posted limit to successfully overtake another vehicle, make no mistake you are driving aggressively.
Some online study aids for passing start with "increase your speed so you may finish the pass quickly" and end with "maintain a safe passing speed until you have created sufficient distance to resume a safe cruising speed." Others recommend a full 10mph speed difference to keep the passing time short.