Jest `--findRelatedTests` runs all tests during lint-staged

Question

I've noticed that our pre-commit script is running too long. After some investigation, I found it is running ALL the tests in the source code, rather than just the tests related to staged files.

I tested by staging a file that breaks a test. When the scripts run, after 4 minutes it gives an error, and the git output shows 1 test suite failed and 356 passed.

I want the pre-commit hook to only run tests against staged files, and thought that --findRelatedTests should do that. Is there an error with my set up?

{
  "devDependencies": {
    "eslint": "8.20.0",
    "husky": "1.3.1",
    "jest": "26.5.3",
    "lint-staged": "8.1.0",
    "prettier": "2.5.1"
  },
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "*.{json,scss,md}": [
      "prettier --write",
      "git add"
    ],
    "*.{ts,tsx}": [
      "eslint --quiet",
      "prettier --write",
      "jest --findRelatedTests",
      "git add"
    ]
  }
}