Offset financial years mean your finance people aren’t working furiously between Christmas and New Years getting the EoY stuff done. I feel bad for the ones in my company every year.
Though it means that some years have 53 weeks in.
Don't they any way?
Well, 52 weeks is 364 days, and a calendar year is 365.5±0.5 days, so if you are doing “years” by whole numbers of weeks and don't want to get more than a week out of sync with the regular civil calendar, you are going to need a 53 week year every few years, regardless of your start date.