In my experience (with vegetarian special meals at least) flying in all class on many airlines over the decades, special meals are essentially the same across classes, just plated and presented differently. In J/F, you may get a slightly bigger portion (or not) and an extra side dish/soup or two. Plus you can partake of the dessert/cheese trolley and fancy chocolates, etc. Most airlines do not bother creating a different version of every special meal for Y vs PY vs J vs F.