We have 3 raid teams in the FC progressing in FCOB. 2 on t12, 1 just started t10. They set it up so that one of the 2 raid parties could, in an example scenario. Team 3 is struggling with mechanics on t10, Team 1 invites there raid leader to train with them. They clear with team 3 raid leader, following week they attempt turn 10 and clear it due to experience raid leader gained with team 1.

That's what it was made for, not to make it easier to sell loot runs.

Working as intended. Clear sellers whining as expected.