This was originally found as an issue with a Terraform provider and a Hashicorp partner found through trouble shooting that there was a bug with the AWS Go SDK: hashicorp/terraform-provider-aws#44095 ...
when using file-system-id as a filter of "aws fsx describe-backups" it always returns empty array. if you use volume-id it works and you can see that the file-system-id of the backup match the one ...