Appstoreconnect API can't query tester installed build

Hey,

I want to check tester's installed app build via Appstoreconnect API, but the BetaTester.Relationships.Builds.Data object in response always return empty array.

{
  "data": [],
  "links": {
    "self": "https://api.appstoreconnect.apple.com/v1/betaTesters/eba48a5b-***/relationships/builds",
    "related": "https://api.appstoreconnect.apple.com/v1/betaTesters/eba48a5b-***/builds"
  },
  "meta": {
    "paging": {
      "total": 0,
      "limit": 50
    }
  }
}

I found a tester who has installed beta app, and the app build info is correct on appstoreconnect.apple.com website.

But through API, this tester's build relationships link data still return nothing.

Is it a bug? 😕

Some screenshots about this problem.

http://antinomy.me/co/test01.png

http://antinomy.me/co/test02.png

http://antinomy.me/co/test03.png

http://antinomy.me/co/test04.png