With the cultural theory, its about playing probabilities.
If you're from the UK, it doesn't mean your tactics will be the same as every other manager from the UK. It just means that there is a most common playstyle. Tactics ultimately are the choice of the manager. And the more skilled the manager, the less likely they are to have their tactics conform to what the dominant cultural system is.
Unskilled managers (or skilled but inactive managers) have a large role in defining this most common playstyle. They don't really understand what does what tactically, but change things around to find what works best. So ultimately, their is a high probability that they'll end up using the tactic that is the most common on their server, or that tactic which counters the most common system. But they don't understand why these tactics are working. So in some cases, some tactics that matchup well against an association opponent, have a poor success rate on some servers, so managers aren't confident in using them when it's the best option for a specific opponent.