That's not all that surprising. Bogleheads are focused on low cost, long term investing based on index funds and its variations. Although some are frugal, that's not always the main ideology.
Mustachians are focused on high savings rates with low cost of living, enabling one to retire early - and most also seem to do index investing.
So in a broad generalization, most Mustachians are likely Bogleheads, but not vice versa... For instance, BH's often discuss the best cars, insurance rates, etc. A true MMM would be ditching the car and getting a bike.
Just because a Boglehead likes to invest in Vanguard index funds doesn't mean they want to retire on 500k and I can understand that. I personally am looking for a few times 500k myself, but to each their own. If you can live forever on 20k - I think that awesome. I just know I wouldn't be able to do that and most folks there might not want that either. But don't take it personally - I typically don't see folks over there being flat out mean...