The reason is rather technical, but I have rearranged the sites slice internally to match the most common sort order for these (for quick indexing), but to sum up:

Currently when you have languages defined with a sort order (weight, name etc.) that does not put the defaultContentLanguage on top, you get:

• site.Languages => sorted by weight, name etc.
• site.Sites => sorted by weight, name etc.

After this fix:

• site.Languages => sorted by weight, name etc.
• site.Sites => default content language at the top, then sorted by weight, name etc.