I really don’t know what to make of this. I thought they were getting better at this sort of thing – having corrected several mispronunciations and improved on some of the accents with the new voiceovers for DE – and I also find it highly unlikely that they both didn’t know how to pronounce ‘Worcester’ and ‘Gloucester’ and didn’t think to look it up. So my guess is that this was done to avoid confusing American audiences – a bit like how Harry Potter and the Philosopher’s Stone has a different (and, ironically, more confusing) title for the American release.
They also mispronounced ‘Acre’ (“Ocker”) and the Welsh accents are not very convincing, but strangely, they seem to have pronounced ‘Llywelyn ap Gruffudd’ correctly.