[Bug]: Jest 30 seems to be 1.5x slower than v29

Version

30.0.3

Steps to reproduce

• Clone the facebook/react repo
• Run yarn install
• Run the tests with yarn test
• Bump jest to v30.0.3
• Run the tests again

Expected behavior

According to the blogpost https://jestjs.io/blog/2025/06/04/jest-30, "Jest 30 is noticeably faster" than the previous versions.

Actual behavior

I attempted an upgrade on two private repositories and noticed that on both of them, jest 30 was slower.

Jest 29: Time: 57.615 s Jest 30: Time: 90.925 s

Additional context

Environment

System:
    OS: macOS 15.5
    CPU: (12) arm64 Apple M4 Pro
  Binaries:
    Node: 20.19.0 - ~/.nvm/versions/node/v20.19.0/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v20.19.0/bin/yarn
    npm: 10.8.2 - ~/.nvm/versions/node/v20.19.0/bin/npm
  npmPackages:
    jest: ^30.0.3 => 30.0.3