Moving forward, yes it is acceptable.
However, didn't the rules always state that it needed to be redeemed for a child meal "where available", but could be redeemed for adult meals from CS restaurants without kids menus?
This is not a matter of closing a loophole, it is changing the rules after both parties agreed to the terms. Yes, Disney reserves the right to make changes, doesn't mean it is ethical to sell one product but provide another.
But isn’t that what everyone was doing, purchasing one product - the child’s dining plan and then using it as another - the adult dining plan? The rules stated that kids needed to order from the kids menu. People just knew it wasn’t enforced so they exploited it. You can’t now call Disney unethical for enforcing rules that were always in place. There are a lot of places to eat at Disney - only a few don’t have kids meals. Use the plan where kids meals are offered or pay for an adult dining plan for the child. Better yet pay out of packet and order them whatever you like.