Mapping an "Authored by" uid fails in the main language

Problem/Motivation

When importing a dual language nodes, with main language set to PT, I can't map a node author:

Authored by (uid): Authored by: this field cannot hold more than 1 values

Steps to reproduce

Create a new feed on a multilang node type.
Set a default lang and author as feed owner (running with ID:1 user)
Map an "Authored by" field and set a fixed value distinct from ID:1, of an existing user
The message appears when importing

If we map an "Authored by" to other language, than it works fine.

it look like feeds is concatenating the mapping uid with the feeds config of having a Feed:owner user and the node owner.

By looking at these threads, I was expecting mapping to override the feeds config.