generateSW() result doesn't match the docs

When using workbox-build I assumed looking at the docs that I would be able to get information about what will be pre-cache from the generateSW() result. See https://developer.chrome.com/docs/workbox/modules/workbox-build#generatesw_mode

When I call generateSW() I get output that looks like:
```
filePaths: [
'.js.map',
'.js',
'.js.map',
'.js'
],
count: 4,
size: 5653385,
warnings: []
```

Is this expected behavior? If so the docs need changed.