REST API for check runs seems to ignore filter=latest

According to the API docs, I should be able to get the latest check run for a build with a given name CHECK_NAME using the following URL:

https://api.github.com/repos/${OWNER}/${REPO}/commits/${REF}/check-runs?check_name=${CHECK_NAME}&filter=latest

However, when I run

curl -H "Accept: application/vnd.github.v3+json" 'https://api.github.com/repos/mit-plv/bedrock2/commits/master/check-runs?check_name=build%20(master,%20coq%20libcoq-ocaml-dev,%20ppa:jgross-h/coq-master-daily)&filter=latest'

I get two builds with that given name, instead of just the latest, so it seems that the option filter=latest was ignored.
Here’s the (shortened) output:

{
  "total_count": 2,
  "check_runs": [
    {
      "id": 1684033230,
      "node_id": "MDg6Q2hlY2tSdW4xNjg0MDMzMjMw",
      "head_sha": "2ac6e6bcb83c206d922636f90fe5edafe3113966",
      "external_id": "28581b6d-9d83-512c-1f72-cc25896368d0",
      "url": "https://api.github.com/repos/mit-plv/bedrock2/check-runs/1684033230",
      "html_url": "https://github.com/mit-plv/bedrock2/runs/1684033230",
      "details_url": "https://github.com/mit-plv/bedrock2/runs/1684033230",
      "status": "completed",
      "conclusion": "success",
      "started_at": "2021-01-11T21:02:22Z",
      "completed_at": "2021-01-11T22:14:31Z",
      "output": {
        "title": null,
        "summary": null,
        "text": null,
        "annotations_count": 0,
        "annotations_url": "https://api.github.com/repos/mit-plv/bedrock2/check-runs/1684033230/annotations"
      },
      "name": "build (master, coq libcoq-ocaml-dev, ppa:jgross-h/coq-master-daily)",
      "check_suite": {
        "id": 1809488584
      },
...
    },
    {
      "id": 1683358423,
      "node_id": "MDg6Q2hlY2tSdW4xNjgzMzU4NDIz",
      "head_sha": "2ac6e6bcb83c206d922636f90fe5edafe3113966",
      "external_id": "28581b6d-9d83-512c-1f72-cc25896368d0",
      "url": "https://api.github.com/repos/mit-plv/bedrock2/check-runs/1683358423",
      "html_url": "https://github.com/mit-plv/bedrock2/runs/1683358423",
      "details_url": "https://github.com/mit-plv/bedrock2/runs/1683358423",
      "status": "completed",
      "conclusion": "failure",
      "started_at": "2021-01-11T18:55:26Z",
      "completed_at": "2021-01-11T18:56:21Z",
      "output": {
        "title": "build (master, coq libcoq-ocaml-dev, ppa:jgross-h/coq-master-daily)",
        "summary": "There are 1 failures, 0 warnings, and 0 notices.",
        "text": null,
        "annotations_count": 1,
        "annotations_url": "https://api.github.com/repos/mit-plv/bedrock2/check-runs/1683358423/annotations"
      },
      "name": "build (master, coq libcoq-ocaml-dev, ppa:jgross-h/coq-master-daily)",
      "check_suite": {
        "id": 1808705523
      },
...
    }
  ]
}

I think that this is a bug, because if I specify a check_name and filter=latest, I would expect that I get at most one check run, namely the latest one with that name. Or does filter=latest have a different meaning?