The police counter is useless

On the contrary, the police counter is incredibly useful, It's possible to use it to tell exactly when it's safe to leave your position during an assault. You can cheese the game just a bit more with a police counter. If I see there are 5 cops on the map, and I see 4 next to me (not possible, but just an example), then I know that I'm safe to go do necessary objectives. That is knowledge that I shouldn't have. It's also why I turned those features off back when I used HoxHud (along with assault phase indicator).

but mostly it is useless too because it's not clever enough to count items that haven't yet been revealed

It's still useful because it alerts you that you forgot a bag, or you can use it to determine whether you've actually gotten everything on the map or not (e.g. I can use the loot bag counter in Shadow Raid to tell if there's coke in the basement without checking the basement).

Both of those give knowledge the player shouldn't have access to, as such, I see them as cheating.

As for gagecoins, it's not cheating in the least. Getting the coins and getting whatever mod you need is no different than rushing jewelry store hundreds of times for the same result. It also doesn't affect your gameplay experience whatsoever if someone else uses goonmod. You literally can't even tell if someone bought their mods with gage coins.

Like, is it possible for you to open someone's profile and say "Oh man, they obviously just used goonmod to get the mods they need?"

And it's not even anything like cheating to V-100. Cheating to the max level gives you an illusion of experience and actually does affect the gameplay of your teammates. Getting some mask cosmetics or a fucking Long Barrel doesn't affect anyone at all.

And it's damn sure nothing like cheating to get all the skills in the game (as that's literally not possible with no game mods whatsoever).

So you can say it's cheating to use gage coins until you're blue in the face, but at no point is your gameplay experience ever affected by anyone using them (which is the real metric we go by here after Overkill said so). As such, we're forced to conclude that it isn't cheating.