Because viewless timeseries collections don't depend on the "view kick-back mechanism" for the read path, the timeseriesBucketsMayHaveMixedSchemaData and timeseriesBucketingParametersHaveChanged flags now also exist on the global catalog, instead of only exclusively on the shard catalog, so that routing can use them.

To support this, running:

db.runCommand({collMod: "myts", timeseriesBucketsMayHaveMixedSchemaData: true})

or

db.runCommand({"collMod": "myts", "timeseries": {
        "bucketMaxSpanSeconds": 12345,
        "bucketRoundingSeconds": 12345
}})

Should set the appropriate flags in the timeseriesFields field of config.collections on the config server.