`parcel build` generates multiple manifest.json when using `package.json#targets`

[mtgto]

I found parcel-reporter-bundle-manifest generates multiple manifest files in the project which has multiple entries.

Parcel provides the way to handle one or more entries.
https://parceljs.org/features/targets/

When using package.json#targets I found parcel-reporter-bundle-manifest generates the number of entries in parcel build .
parcel serve generates one manifest file.

$ cat package.json

{
  ...
  "targets": {
    "a": {
      "source": "a.js"
    },
    "b": {
      "source": "b.js"
    }
  },
}

$ yarn run parcel serve
$ cat dist/parcel-manifest.json
{"a.js":"/a.js","b.js":"/b.js"}

$ yarn run parcel build
$ cat dist/a/parcel-manifest.json
{"a.js":"/a.js"}
$ cat dist/b/parcel-manifest.json
{"b.js":"/b.js"}

It is not occured while using package.json#source to give multiple entries to parcel.
It is In My Opinion, but it should be generated one manifest.json file.

---

Reproduce code↓
https://github.com/mtgto/example-multi-entry-parcel-reporter-bundle-manifest