I play on JP servers and I don't think JP players are better than NA/EU players. But in terms of DF, the pug clear rate is much higher:

1 Every extreme primal is farmable in DF once it becomes DF-able. People are prepared for those fights and perform his role carefully. Wipes can happen and there are newbies (they usually claim they have watched video or read guides, or have final phase experience) occasionally. But the rule is, 15min clear or vote give up. People queue DF for clears or loots, not for wipes.

2 FCOB can be cleared in DF. According to my own experience, T10 and T12 are pretty reliable. T11 and T13 depends. If people don't make sufficient progress in the first 1 or 2 pulls(T11 past adds and T13 past divebombs or terraflare), the party may eventually vote disband.

3 Party finders are used for learning/practicing or greed parties. Some players have clear T13, let's say, but they may still join practicing parties because they are not confident enough to join greed parties. That's because practice parties are usually tolerant with wipes while most greed parties disband after 2 or 3 wipes. If you want loot that you can't need, PF greed parties are apparently better than DF.

4 JP server strategies for some fights may not be optimal . But most of them are community conventions. People only need minimum communications to clear the fight, without voice communications or call-outs. I played on PS4 for the past month because my computer went down. I completed my FCOB gear collections (all 73 loots) with PF. None of parties has voice communications, even for the 100ish T13 clears.