Or it shows that there is not one region where people only use Northern words, and another one where people use only Southern words, and never the twain shall meet...
I've heard the number "five or six" for the number of main dialects in Wales, and this N/S thing seems to be a tendency -- so it would not be surprising for an area to use some "Northern" and some "Southern" words.
Like a lot of European languages Welsh distinguishes familiarity in the 2nd person.
Ti - use with close friends, close family, children, animals, God. Ti can only be used in the singular, never plural.
Chi - use with anyone not in the Ti list. Chi can be singular or plural.
Wyt and dych are the same as dw and mae and are simply the verb "to be".