Oh not it's not. Definitely. (Not definately).
Unless your're talking about the 'township' of Wigan, an outdated concept which now has only limited relevance in some very rarified legalistic aspects of life today and which was based on the former 'parish' boundaries. That would be a bit pedantic, eh?
I'm talking about every other parameter: closeness to the town centre, postal address, common usage,etc.etc. etc.
And what 'people' generally understand and mean by 'Wigan', which is the most important factor in communicating an idea.
Everybody except you knows that Galloways is in Beech Hill, and Rollin Pin is in Newtown, and both of them are in Wigan.
And Galloways pies are rotten, while Rollin Pin's are delicious.