base64: Unexpected result when decoding data with garbage

Hi,
I have run in to a problem when trying to base64 decode a file that contains garbage data. This is with the coreutils version 0.8.0, installed from the Ubuntu 26.04 Resolute apt repository.

Consider the following truncated content from my_base64_file.txt:
eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiJjMjQ5MmF

Yes! It contains a ., which is garbage. I know.

When decoding it with base64 (GNU coreutils) 9.4 the result is:
base64 -d my_base64_file.txt --> {"alg":"RS256","typ":"JWT"}base64: invalid input
base64 -di my_base64_file.txt --> {"alg":"RS256","typ":"JWT"}{"jti":"c2492abase64: invalid input

But, with base64 (core uutils 0.8.0) I get:
base64 -d my_base64_file.txt --> base64: error: invalid input
base64 -di my_base64_file.txt --> base64: error: invalid input

Is there something I am missing here, or is there a bug with the --ignore-garbage feature?

Start by reproducing the documented base64 -d and base64 -di commands with the provided input, then trace the base64 command's --ignore-garbage handling. Done means the behavior matches the reported GNU coreutils results, including decoded output and the invalid-input diagnostic.