The tag is present in Lintian version 2.109.3. That is the most recent version we know about.
The source tarball contains a prebuilt binary wasm object. They are usually provided for the convenience of users. These files usually just take up space in the tarball and need to be rebuilt from source.
Check if upstream also provides source-only tarballs that you can use as the upstream distribution instead. If not, you may want to ask upstream to provide source-only tarballs.