Why battlecruisers counted as dreadnought-type capital ships

Why could HMAS Australia be counted among Dominion dreadnoughts when she was a battlecruiser rather than a battleship?

Because contemporary usage treated battlecruisers as dreadnought-type armored cruisers and battleships as dreadnought-type battleships, with both belonging to the new capital-ship category.

Period usage included both dreadnought-type battleships and dreadnought-type armoured cruisers. HMAS Australia was a battlecruiser and could therefore count within dreadnought capital-ship totals. Restricting the term to battleships would exclude a category that contemporaries included from the beginning. Fisher's role in creating Dreadnought and the battlecruiser concept supports that broader use of the terminology.