For me it is shocking in a way....

I have been stopped by the men in blue quite a few times, but I always did something wrong when they stopped me, I've never been stopped without a reason.

OP, are you 100% sure your light was green (I bet you are) and are you sure there wasn't an unsolved matter from a few days before? I vow for the fact these guys have memories like elephants. I once was on a van from Ratanakiri to Phnom Penh when the van was assaulted on the border between Kratie and Tbong Kmoum provinces because the driver didn't stop when they (the guys in blue) tried to make him a few days earlier. They weren't easy on him and I can vow for the fact the driver didn't make any money that day despite having a van full of passengers.

I would say that the North Norodom police along with the Mao Tse Tung/Great Joke Hotel police are probably among the tightest & generally better to avoid if at all possible. That said I've often gone by both without drama on my bike which is a Harley, with baffles still inserted - i.e. not as noisy as the straight pipe folks.. but still, waiting for either of those crews to pull me in. I did notice both of those police tend to stop locals on every light change, so it isn't personal against foreigners.

The only incident I had with the MTT guys was in the car years back though, I went through a green light that turned amber at the last split second I could still see the light (yarly!) and they hooked me in. No big drama, just made me 10 mins late for work.

Riding Toul Kork to South Monivong daily through numerous police I haven't been stopped for nearly ten years best guess. #TouchWood

I got stopped on monireth and Sihanouk, heading towards stung meanchey. I was sure it was still amber, but they produced photos of me having passed the road divider (their definition of legal- if you've passed the end of the road divider on yellow, but oncoming traffic has not yet ceased, you can still go) whilst it was already red. We're talking fractions of a second here. Anyway, I become passive aggressive and insist on paying the 10 bucks via ABA only. None of the cops have ABA at first until the stalemate reaches about 4 minutes. Then one cop produces an ABA account number for a 'coffee shop'. I say OK, that's your wife's account isn't it? Now I know your wife's name. What's the coffee shop? Where is it? I'll go have a coffee with your wife! This made him visibly awkward which was a small victory. Money paid, and now they acted like my best friends asking questions from the usual script about time in Cambodia, wife, any kids etc. You speak khmer very well, La La La.

This is Bali, but could be a good little earner for you digital nomads in Cambodia!

Well! I for one won't stand for it!
Call the cops. They'll know what to do.