This is in no way unique to IBM manuals.
The phrase is present in loads of books and in some cases has been for quite a few years.
https://meh.com/forum/topics/nothing-is-lacking-the-long-history-of-intentionally-blank-pages
https://www.google.com/search?q="this+page+intentionally+left+blank&udm=36
Python is an interpreted language but for a compiled language absolutely (and obviously).