As can be seen, fuel contamination can affect both engines as seen by the EPR fluctuations on both engines. Is there anything else that could cause unusual indications on more than one engine. Maybe icing conditions where the anti-ice was not applied pops into mind. Volcanic ash. Anything else to consider in such a scenario.
Like you said ice-crystals at altitude or volcanic ash probe blockage.
All this is covered in the FCOMs.
If the fuel SAP problems become more frequent there is always the possibility that somebody could update the manuals. I'm not very keen on the crew trying to decipher it, but the FADECs probably could.
The problem, to me, is that there is not much the crew can do about it other than what these guys did.
What happens in the air is not the problem, it's what happens when you try and land. I would like to have the equipment standing by on a long runway being prepared for an excursion.