I happen to have the temp versus station diagrams for the GEnx and the T1000 (I analyze engines over at !!!!!!!!!!!!!!) so I thought I post them here as well, here the link to the Airlines post:
How Does A Software Change Solve Icing Issues? — Tech Ops Forum | !!!!!!!!!!!!!!
The diagrams show very clearly why a 2 shaft booster engine can have the type of icing problems discussed and why a 3 shaft is less affected. First the GEnx-1B:
Then the T1000:
As said these are the design point diagrams,top of climb in these cases. The cruise temps will be somewhat lower, the ToC thrust is around 17klbf and the typical crusie thrust around 10-12klbf at FL350 and higher.
Now one can see that there is low temps before the HPC in the 2 spool as the booster works with very low pressure rise (less then 1.5 in cruise) and hence temps, the temps might just be enough for the thawing and refreezing cycle discussed. The 3 spool is cold until the IPC comes and then it raises the temp fast as it works with optimal RPMs (the booster spins with the fans low RPM), hence the ICI does not thaw until they thaw completely and don't reattach.