I stand up all the time to stretch out. Never had a problem in BC. I've only ever been pulled over once on a bike in hundreds of thousands of kilometres and that was because I was riding the shoulder. I doubt 99% of the cops are even aware of the law (that law, in particular, I mean).
I expect that when this gets to court it will either be thrown out or greatly reduced (assuming circumstances are as stated) but that doesn't reduce the cost of having to go to court to get it done. All it takes is lack of common sense on the part of the LEO and then it is up to the rider to try and undo it.
As to whether the police are aware of it..... if they are all not, how can it be expected that the general public be?