Next.js 16's Turbopack is 2.5x faster, but the bundler is only 4% of your build

Next.js 16 makes Turbopack default and claims 2-5x faster builds. On a 60-route app it held, but on a warm build the compile is 143ms of 3.45s, and half of webpack's build is a 6.6s phase nobody benchmarks.