Tom, I will endeavor to find out why PB have that p26 sketch and where they got it from. If Neil Crafter sees this then Neil, can you confirm it's not an error before I go barking up the wrong tree?
I agree those drawings all look to be different. I believe the one of Yarra Yarra on p23 is Russell's. I have seen it attached to a newspaper article by J.M Dillon (Sporting Globe Dec 17 1927) as the course was nearing completion. The article talks about Alex Russell as the designer of the links.
The style is quite similar to the plan on p101 of Joseph Johnson's "RMGC - A Centenary History" book which is credited to Russell. The one of the Flinders links on page 88 of Tom Doak's MacKenzie biography, looks similar again, but we know from AM's letter that Alex did do some of his plans:
"Moreover, since I arrived here Mr. Russell has been continually associated with me while I have been advising golf clubs, and he has not only drawn some of my plans but has made many valuable suggestions". -AM
I was going to say that the two green sketches of Lake Karrinyup on page 25 look like MacKenzie's, but if they were done in 1948 that would be impossible