I disagree:

    good:
      - a
      - b
      - c

    bad:
      - a
        - b
      - c

Obviously when I show you this, it's clear that b is incorrectly indented, but in a real file, this can be a nightmare to figure out. Particularly if the entries are nested, or tab characters are involved.

Meanwhile, the error in JSON is way more obvious:

    {
      "good": [
        "a",
        "b",
        "c"
      ],
      "bad": [
        "a - b",
        "c"
      ]
    }

Not really, i think yaml have more capability, you can convert json to yaml 1:1, but the reverse isn't true.

But here is the issue: the errors caught in a json-validate won't be in a yaml-validate. If you have 15 inventory file to write per day, you will do a lot of copy pasta, sometimes with errors, and most of those times ansible won't resolve because the yaml was obviously false. The one time it wasn't, it was sadly on a critical part of our infra, and almost cost us a client (and definitely costed trust).

Yaml is way more permissive (because it has more capabilities). But we didn't care about map and semi-code or whatnot. If you need it, more power to you, it just wasn't our original usecase. So they wrote some perl json->yaml interpreter with restricted keywords, and after that, the misalignment risk was negated. Ultimately i arrived at the company, was told the story, then wrote stuff to convert excel->json, then SQL->json, and effectively in the end the extra conversion was unnecessary, and probably harder than just converting directly in yaml. I'm not saying yaml is worse than json, i think in 80% of cases, it's better. I'm just saying that in the rare cases where being correct is way more important than being fast, i'd use json.