We don't have a cross-reference for "swap", either, so adding one for [array.tuple] makes the presentation inconsistent. (We do have a cross-reference to the superordinate subclause at the start of the header.)
@zygoloid, which way do you want to go here? Add detailed cross-references in synopses whenever we have subclause headings? Or don't bother for small headers?

You are right. I must have done this because pair does it, too.

Editorial meeting:

• Cross-references are useful; cases that are missing are bugs.

Does that include cross-references to the containing subclauses that group cross-references? For example, [concepts.syn] and [algorithms.syn] first cross-reference the containing subclauses of the described concepts/algorithms. This is applied inconsistently.