yotty
nice catch. Short of conclusive, but certainly tracking well (it would seem), to the end result. The terminology is not yank so I infer the "Coupling interface" to mean a thrust bearing.
Thrust, received by the face of the Shaft's shoulder, and negative thrust, if the engine is barfing, must be absorbed through a range of values, including vibration and high energy harmonics. The AD is a follow on to an original, perhaps not in time to preclude this event, even though the inspection alone creates problems relative to mitigation, and might be under "Pressure" to be declared "Deferrable".
Any repair would be a replacement of the disc and possibly the shaft. Time consuming, and expensive, to include a/c out of service. Leases don't take vacations.
I have seen a Shaft set of splines rub the disc face smooth, (generally the Shaft metal is treated to be more wear resistant than the disc hub). If a lubrication issue, flow restriction is necessary of the designed kind, but coking and carbon are not in the design consideration.
Is this about what you had in mind?
bear