egafd.com

The extreme SW is known as "Little England Beyond Wales". If you Google you find articles like
But I don't know if that explains your linguistic experience. I've never heard of that before.
Cardiganshire is the centre for jokes about being careful with money/meaness. E.g. A "Cardi" casts his bread upon the waters but only when the tide is coming in.

Mart

I found a big divide between North & South Wales myself.
The North closed and cold whereas the Southerners were friendly and nosey.

Perhaps that's just me.

The Northerners were more reserved than the Southerners. But I understand that one keeps distant from a foreigner that speaks a sort of English one can't make head nor tail of and says three when he means four.
For us not being understood was a strange experience, at least in the UK. In the other parts of the UK we have visited (London, Rochester, York, Cornwall and Scotland) communicating with the locals never was much of a problem.