You are quibbling with the terminology, and it makes it more confusing for people to understand.

They will all be possible hets. They will all be possibly double hets. How much of a possibility is there? 50% for each trait!

THEREFORE:

50% double hets for X and Y.


Now I understand where you are coming from with the percentages, but you are making it much more complicated with percentages than is necessary, IMO.

Yes, the actual chance for them to be double het is 25%