Error migrating legacy index templates to composable

[Bob_Penrod]

I'm running into errors on ES 7.17 migrating "legacy" index templates to the new composable style.
Given the following two templates, creating the 2nd gets an error:

PUT _index_template/test_template_1
{
  "index_patterns": ["test.*.env1.*"],
  "template": {
    "mappings": {
      "properties": {
        "created_at": {
          "type": "date",
          "format": "EEE MMM dd HH:mm:ss Z yyyy"
        }
      }
    }
  },
  "priority": 0
}
PUT _index_template/test_template_2
{
  "index_patterns": ["test.*.env2.*"],
  "template": {
    "mappings": {
      "properties": {
        "removed_at": {
          "type": "date",
          "format": "EEE MMM dd HH:mm:ss Z yyyy"
        }
      }
    }
  },
  "priority": 0
}

the error is

index template [test_template_2] has index patterns [test.*.env2.*] matching patterns from existing templates [test_template_1] with patterns (test_template_1 => [test.*.env1.*]) that have the same priority [0], multiple index templates may not match during index creation, please use a different priority

However, if I make the priority in one of the templates different from the other template and then create indices against them, I can see that those index patterns do not conflict.

For example, if I do PUT /test.4.env2.1234 then test_template_2 will match even if it has lower priority than test_template_1. So, the index patterns don't conflict, right?

What am I doing wrong?