Unless you have the source code and are looking at the defined functions for the accuracy or whatever it would be called, you can't really know how things behave.
I have noticed that MGs suppress much worse if slightly behind some large cover like a car. You can notice it by looking at all the bullets that hit the large object in front. Even though some say that small arms fire does not have any collision data and does not behave like tank shells. I've also noticed that KT pintle MG in spearhead, and MGs in buildings suppress almost instantly, even against green cover. Confirmed it on Across the Rheine by building sandbags, putting 4 man IS behind them perfectly, and using that large top-left building (below the top fuel) to shoot at the Infantry section. They got suppressed in one volley and I noticed that the MG was positioned on the 2nd floor (so the tracers could easily be seen going directly onto the IS, rather than the sandbags).
So nobody except Relic really knows. Hence why you have bugs like JP4 shooting across the map, killing an ambulance.
You can open the attribute editor and check all the variables that are defined somewhere inside the source code, but unless you see the functions themselves, you will never completely know. You can only assume and deduce.
As I have already pointed out to you KT Pintle does not suppress only the hull mg does:
Name: "Spearhead"
Duration: Toggle Ability
Cost: Free
+50% sight range.
-25% speed.
Hull MG's will deal 2% suppression.
Locks the King Tiger's turret to a frontal 90 degrees arc.