My understanding is that the 116 series of Alfas had cast iron valve inserts in the Alloy head and theoreticallywould be prone to valve recesion.
Of course how long it takes to cause a problem is another matter.
In fact it will probably take several years before it becomes a problem.
The alternative is to use 98 ron and put in an additive. (assuming available)
You do not really have to put it in every fill ,so if he forgets it doesn't really matter. But if you do use an additive it should be the same type as what was in the petrol he was normally buying as mixing additve types (not brands) can increase valve recession.
By type I mean chemical type as there are several different types of additives used.