That page has been pointed to several times around here.
It's probably the worst examples of PBP programming found anywhere on the internet.

Sure, the programs are smaller when you use some of those techniques.
But the savings come from bypassing the normal bank switching and page bit setting that PBP does to insure everything keeps working properly.

The examples are fine by themselves because they are never larger than 2K and variables are never outide of bank0.
But when you try to use them in your program that is bigger with more variables, all hell breaks loose.

There are a couple true statements on the page, but with so much bad advice, it's hard to find them?

My advice is to delete that bookmark from your favorites, and forget what you read.

In his defense, ... it was 2002. I had some strange ideas about PBP back then too.