Animal Well wouldn't exist without Handmade Hero, Billy himself said it in an interview. The first game architecture he made was RAII etc and full of spaghetti and then he actually followed Handmade Hero and started to getting somewhere.

To be fair, there's another adage that comes into play here: Build one to throw away, you will anyhow.

His second attempt, no matter how he made it, was made with the context of his earlier mistakes.

RAII doesn't lead to spaghetti code necessarily. If anything, "unity builds" would more encourage spaghetti as it's easier to reference anything else in your build.