There are in fact over 2,400 secondary spelling variations contained in Microsoft Office, including words such as organise/organize, focused/focussed and mum/mom. There are also words which are spelt incorrectly such as snorkeler, and the correct spelling snorkeller needs to be added to the dictionary.
The preferred Australian English spelling files correct this shortcoming of MS Office on both Windows and Macs, in Internet Explorer 10/11, and in development is a native dictionary for OSX which works with Outlook 2011 and native applications on the Mac.
For some the preferred Australian English spelling simplifies the language and for others produces documents with less errors. If spelling is an important part of your life or business, consider checking out my work at www.Australian-Dictionary.com.au.
Creator of the preferred Australian English spelling dictionary.