It's just the "normal/heroic raiders" who tries to imply that there is a substantial difference between LFR, normal and heroic raids.
Anyone who has played this game a few expansions, know how this tune goes.
But OP is right, its totally bullshit that you can't do the mentioned quests in LFR, completing the artifact should be more available than legendaries.
Throwing digressions about other difficulties is not discussing the OP's statement in any shape or form.