azure-devops - Azure DevOps server import pipeline functionality ignores Approvers definition

Question

I have the following definition in my pipeline that I am running on Azure DevOps Server Version Dev17.M153.3

After saving the change I can see the following content has been added to pipeline definition

"approvals": [
          {
            "rank": 1,
            "isAutomated": false,
            "isNotificationOn": false,
            "approver": {
              "displayName": "Aouslender, Alexey",
              "url": "http://tdc1tfsapp01:8080/tfs/DefaultCollection/_apis/Identities/2d86d86b-fe02-4e22-aa53-4315cdb3821c",
              "_links": {
                "avatar": {
                  "href": "http://tdc1tfsapp01:8080/tfs/DefaultCollection/_apis/GraphProfile/MemberAvatars/win.Uy0xLTUtMjEtMzMwNDk4NzQ2Ni0xODkxMDA3NDIzLTI5MjUxNTc3OTctNDU4NDA1"
                }
              },
              "id": "2d86d86b-fe02-4e22-aa53-4315cdb3821c",
              "uniqueName": "DOMAIN\\PXXXXXX",
              "imageUrl": "http://tdc1tfsapp01:8080/tfs/DefaultCollection/_apis/GraphProfile/MemberAvatars/win.Uy0xLTUtMjEtMzMwNDk4NzQ2Ni0xODkxMDA3NDIzLTI5MjUxNTc3OTctNDU4NDA1",
              "descriptor": "win.Uy0xLTUtMjEtMzMwNDk4NzQ2Ni0xODkxMDA3NDIzLTI5MjUxNTc3OTctNDU4NDA1"
            },
            "id": 3546
          }
        ]

Now I am exporting pipeline, using export option. Then I am deleting pipeline and importing it using exported json file. The imported pipeline missing the Approvers definition, nevertheless I can see the definition in exported json.

"preDeployApprovals": {
                "approvals": [
                    {
                        "rank": 1,
                        "isAutomated": false,
                        "isNotificationOn": false,
                        "approver": {
                            "displayName": "Aouslender, Alexey",
                            "url": "http://tdc1tfsapp01:8080/tfs/DefaultCollection/_apis/Identities/2d86d86b-fe02-4e22-aa53-4315cdb3821c",
                            "_links": {
                                "avatar": {
                                    "href": "http://tdc1tfsapp01:8080/tfs/DefaultCollection/_apis/GraphProfile/MemberAvatars/win.Uy0xLTUtMjEtMzMwNDk4NzQ2Ni0xODkxMDA3NDIzLTI5MjUxNTc3OTctNDU4NDA1"
                                }
                            },
                            "id": "2d86d86b-fe02-4e22-aa53-4315cdb3821c",
                            "uniqueName": "DOMAIN\\PXXXXXX",
                            "imageUrl": "http://tdc1tfsapp01:8080/tfs/DefaultCollection/_apis/GraphProfile/MemberAvatars/win.Uy0xLTUtMjEtMzMwNDk4NzQ2Ni0xODkxMDA3NDIzLTI5MjUxNTc3OTctNDU4NDA1",
                            "descriptor": "win.Uy0xLTUtMjEtMzMwNDk4NzQ2Ni0xODkxMDA3NDIzLTI5MjUxNTc3OTctNDU4NDA1"
                        },
                        "id": 3535
                    }
                ],
                "approvalOptions": {
                    "requiredApproverCount": null,
                    "releaseCreatorCanBeApprover": true,
                    "autoTriggeredAndPreviousEnvironmentApprovedCanBeSkipped": false,
                    "enforceIdentityRevalidation": false,
                    "timeoutInMinutes": 0,
                    "executionOrder": 1
                }
            }

Am I missing something here or is it actually a Microsoft bug?