Pivot Charts behave different in Date formatting

So in attached sample book I have 2 graphs which both have their data sheet.
On both data sheets a pivot is based with a pivot chart.
Both sheets have a date field that cannot be formatted in field settings (due to blanks I guess).

However when I format the date field in chart 1 to 'Mar-12' it will show the same format in the graph.
But when I do the same in chart 8 then the pivot will show 'Mar-12' setting but the pivot chart will not!

Anybody know what is going on here?