“Put in another way - you could argue that the Canadian Red Ensign was a de facto National Flag from around 1892 onwards, but you could never argue that it was a de jure National Flag.”
It’s a core part of Canadian heritage. Same with the Australian flag.
That may be so. I'm not a Canadian, though, so I don't presume to tell Canadians what they should think on this issue.
If Australia hadn't got around to designing a national flag until the 1960s, I think ours would be different than it is.