The problem, I think, comes from people using RAW and RAI in a different way from what the devs intend. Everything in the book is - by definition - written, so everything in the book is RAW. Now, the devs themselves don't make differences about what it's in there, they call everything rules and everything guidelines, and considering that everything is flexible anyway for any given DM, it makes sense. Some will consider some sections of the book as rules, others as guidelines, who cares ? Actually, there is only one type of person who cares, more about this below.
The RAI is defined by the devs themselves as "what the designers meant when they wrote something", but again, first no difference between rules and guidelines, just between what has been written and a possible interpretation of it. But even if you make a difference between a rule and a guideline in the books, I think it's clear that it's as easy to determine the intent from a rule than from a guideline, actually more so.
Also note that, from the dev "In a perfect world, RAW and RAI align perfectly, but sometimes the words on the page don’t succeed at communicating the designers’ intent." And that's it.
So I think it's a bad idea to consider some sections of the books as RAW and others as RAI, it's clearly not aligned with the definition, and by doing it you would just start another semantic war.