That's why I asked for people who had the experience or had asked to do something similar rather than quoting rules.
Just last January, LH was able to check through my luggage CDG-FRA-IAD. CDG-FRA was an award ticket, and the FRA-IAD was a revenue ticket operated/ticketed by United. I know it is not the same example, but when I ask in this forum, I receive multiple responses quoting rules saying it was impossible.