WojtekSz
No. Not "fluid" drive in the sense of "Hydraulic", where the medium is contained. The Gas Path does have open ends at either end, so technically it does not qualify. In addressing this problem, the "Rigid Coupling", it isn't relevant, imo. The Vibration (causatuve of rupture) had alot of time to act on the weak portion of the design, even at that both Disc fractures occurred on climbout, and one of the Powerplants was a TRENT 700. The identified problem was not embraced by RR at any time, whether inadvertent or some thing more diabolical. They have the benefit of the doubt, as far as I am concerned. That covers the Design, Test, and Certification modes. What the firm did after the Burst/Explosion is inexcusable, keeping a client (QANTAS) in total darkness, while they casually (and cynically) completed newer Airframes for delivery. They allowed the Engines to "Time In" because they had duped EASA into relaxing the Inspex. Even in that, they almost made it.
They will correct, and move on. Hopefully, the fallout from their self sabotage will hurt deeply, suffiicient to caution themselves and others against playing Roulette with the lives of paying innocents.