IoT core greengrass fleet provision device side effectiveConfig.yaml does not have updated thingName

Trying to use provision by claim and provisioning hook to admit the device. The provisioning hook output will return a formatted thingName rather than the name passed into the provisioning hook,

const requestedThingName = input.parameters.ThingName;

....

const output = {

    allowProvisioning: True,
    parameterOverrides: {
        ThingName: newThingName,
    },

this works, but on the device side, after iot mqtt session successfully established, in /greengrass/v2/config/effectiveConfig.yaml, the file looks like this:

system:

certificateFilePath: ""

privateKeyPath: ""

rootCaPath: ""

rootpath: "/greengrass/v2"

thingName: ""

services:

aws.greengrass.FleetProvisioningByClaim:

configuration:

I would expect, updated thingName is there under thingName key.

I can only see the newThingName in config.tlog: {"TS":1649181903995,"TP":["setenv","AWS_IOT_THING_NAME"],"W":"changed","V":"newThingName"}

I think effectiveConfig.yaml should be updated.