One advantage that isn't mentioned in the article: code examples. As a monorepo grows, it's more likely that someone else using the repo somewhere has attempted

One advantage that isn't mentioned in the article: code examples. As a monorepo grows, it's more likely that someone else using the repo somewhere has attempted to do the same thing that you want to do, and you can use tools like searchcode to easily find usages and see how they did it. Often this works better than documentation, which for internal projects tends to be non-existent or out-of-date. One disadvantage: a lot of IDEs don't cope well with monorepos as they try to index the entire thing.