Y only policy is becoming more and more common.
Our firm is a huge multinational and changed the policy to Y only for all. Previously, executive level employees could fly J if the journey was over 6 hours. I suspect at a smaller firm, the policy will be more flexible.
I agree with the suggestion above to leave it until later in the negotiations. Don't bring it up as a point until you've already convinced them that you're the one they want. At that stage, it's far easier to spring in a few extra demands without scuppering the whole job.