The yolk affects taste, color and texture. I'm not sure what more you could demand from an ingredient. No one has "arbitrarily" picked a single ingredient to d

The yolk affects taste, color and texture. I'm not sure what more you could demand from an ingredient. No one has "arbitrarily" picked a single ingredient to define real mayonnaise, you'd have the same reaction if someone tried to replace the vegetable oil with lard, or the vinegar with sulphuric acid. The basic recipe for mayonnaise is pretty uncontroversial. As for having the same taste, I'll believe that when I taste it. That's what Coca-Cola says about Zero as well. It's just marketing, they're not going to say that the product they're passing off as real mayo doesn't taste like mayo.