I would be upset especially if I were paying full revenue for the flight. If they had warned us before boarding the flight I would have asked if I could be accommodated on a flight with the full "First Class experience".
A Y meal and a J meal is different just like going to Morton's Steakhouse and being told "I'm sorry sir but we ran out of the steak would you like a steak from the Outback Steakhouse? Of course I would not take their offer.
I would hope you were given hefty compensation for the downgraded service or at least given the option to take another flight or be refunded miles to use on another flight with the full service.
How can an airline give the Y meal in a premium cabin? Just be glad it wasn't the cat food from Stogel's Kosher catering. Gee anything is better than a Stogel KSML.
But still why would you pay a premium price only to get a Y meal. I mean at least you got food but not what you had anticipated.
I wonder what if they just gave everyone J meals even in Y so the Y cabin would get a better meal and the J cabin would still get their meal.
When you have a shortage of a meal why not just give everyone the J meal and then be done with it? Hey you never know there may be a Y customer who would want to fly in Business Class after learning they got an upgraded meal. It's a win-win situation. In the end it could save the airline money from offering the compensation.
Has it ever happened that an airline could not cater the Y meal and gave everyone a J meal? That would be fun to see the Y cabin getting J meals.