it was in a collection that was first published 1918.

But Henry Lawson wrote it in 1896. (See here) Which of course doesn't mean that the Great War wouldn't have given it a new relevance and poignancy, and that would have been a reason to include it in a 1918 collection.

I much prefer Lawson's "Len's a match" to the amended version - "No one could be his match". I suppose that's got the merit of being easier to understand in places where people don't use the expression - but it goes against the sense of them all being equal, and it's just that this is the one who is being seen off today. It sets him up as a hero, rather than as a mate.