pg_decode_message vs skip_empty_xacts and xact_wrote_changes

Hi All,
Every pg_decode routine except pg_decode_message  that decodes a
transactional change, has following block
/* output BEGIN if we haven't yet */
if (data->skip_empty_xacts && !txndata->xact_wrote_changes)
{
pg_output_begin(ctx, data, txn, false);
}
txndata->xact_wrote_changes = true;

But pg_decode_message() doesn't call pg_output_begin(). If a WAL
message is the first change in the transaction, it won't have a BEGIN
before it. That looks like a bug. Why is pg_decode_message()
exception?

-- 
Best Wishes,
Ashutosh Bapat