[BUG] backupconfig/vaultconfig update not working as expected

[Klaas-]

API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/recoveryservicesbackup/resource-manager/Microsoft.RecoveryServices/stable/2025-02-01/bms.json

API Spec version

2025-02-01

Describe the bug

Lets say I want to update the soft delete retention period of a vault.

https://learn.microsoft.com/en-us/rest/api/backup/backup-resource-vault-configs/update?view=rest-backup-2025-02-01&tabs=HTTP#code-try-0

PATCH https://management.azure.com/subscriptions/xxxx/resourceGroups/yyyy/providers/Microsoft.RecoveryServices/vaults/zzzz/backupconfig/vaultconfig?api-version=2025-02-01

With body:

{
  "properties": {
    "softDeleteRetentionPeriodInDays": 18
  }
}

Returns 200 (as in it should have succeeded)

but instead of changing anything the call does nothing.

Expected behavior

Changing the soft delete retention period

Actual behavior

nothing changes

Reproduction Steps

curl or use the web page in description

Environment

Edge / RHEL8 curl

[Klaas-]

Also the location of the vault should be returned, but it's not being returned