I don't think this is across the board. I've traveling to PRG with my wife this fall. I got her an XF ticket OK. Worked hard to get a biz ticket for myself. To keep it below $5000 OGG-SFO-FRA-PRG, had to get coach OGG-SFO-OGG. Got a Z fare SFO-PRG. However, for my return in Oct, I had to get a different flight than my wife, as 901 didn't/doesn't offer any Z fare when I've looked. I'm on the LH flight, she's on the UA flight. Hoping "O" opens up on my flight and I can move her onto it, which would allow us to use the LH FCL/FCT at FRA. Not there yet, however.