I don't think you're missing anything - but that's why I also stick to the limit through average cameras! However - I stick to the limit as measured by a) my GPS device, and b) the average speed functionality in my car's trip computer - those two agree and indicate a higher speed (by 3-4 mph) than the speedometer, so that's what I stick to. As I've not been pinged in roadworks (touch wood), I think my strategy is valid.
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p