while writing a script that links related files via meta-data i found that meta-data lookup by key works in batch mode, but meta-data storage by key doesn't

my scripts output was lines like:

{"key": "SHA256E-s13238976--7f9f459b99e36e9d50e6da349258525c9f63a33bd5f5bf5a3284cc0e4bda5fd8.ARW", "fields": {"linked.image": "SHA256Es3983492--0fef9eba38c21629e2ae06bd7f64dae104d8576e3c4d31b2caf7337a1ed8c3a9.JPG"}}
{"key": "SHA256E-s3983492--0fef9eba38c21629e2ae06bd7f64dae104d8576e3c4d31b2caf7337a1ed8c3a9.JPG", "fields": {"linked.raw": "SHA256E-s13238976--7f9f459b99e36e9d50e6da349258525c9f63a33bd5f5bf5a3284cc0e4bda5fd8.ARW"}}

and the full pipe was

 git annex info */*.* --json --fast| python3 ./check_has_all_raws.py |git annex metadata --batch --json

to my surprise all i got was the retrial of the existing meta-data instead of the addition of the linked fields

IHO git annex should allow to store metadata in batch mode by key