Yes, of course it is discriminatory. But not in the PC sense (which I hope is not what you are suggesting). Special meals are pre-ordered and loaded based on specific requests from passengers. Last minute upgrades for operational reasons are fully at the discretion of the airline and no special meal passenger or status card wielding traveller has any more claim to this treatment over any other. I can't think of any airline which promises a certain group of passengers priority treatment in such instances over any other. Airlines will obviously upgrade those whom they can accommodate more easily (solo travellers, no special meals, no special seating requirements, etc). This would apply for upgrades (operational or not) made more than 24 hours in advance as well. It's at the airline's discretion, so why bother with the complicated passengers when you can just select the easier cases. I suppose it's a price you pay!