Describe the bug

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 requested by the file-system-id filter.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

the API should return all the backups of all the volumes of the file-system-id

Current Behavior

returns:
{
"Backups": []
}

Reproduction Steps

• create FSx Ontap
• create svm
• create volume
• backup the volume
• try to run: aws fsx describe-backups --filters '[{"Name": "file-system-id","Values": ["fs-xxxxxxxx"]}]'

Possible Solution

No response

Additional Information/Context

No response

CLI version used

2.31.0

Environment details (OS name and version, etc.)

aws-cli/2.31.0 Python/3.13.7 Darwin/24.6.0 exe/arm64