Posting to RDA-L
Concerning the default procedure for collective titles, the LCRI says:
“Except as noted in LCRI 25.9 and LCRI 25.10, assign a collective uniform title to an item at the first instance of appropriateness, e.g., do not defer the adding of a collective uniform title until the file under the heading is voluminous.”
“25.8-25.11. Collective Titles”
There is also LCRI 25.10. “Works in a Single Form”
“Rule 25.10A applies to collections of three or more works in one form when the author writes (or is assumed to write) in two or more forms. The purpose of the rule is to provide a sensible gathering point in the catalog for items whose titles are more or less inadequate. Thus, if a collection covered by 25.10A has an adequate title, the rule should not be applied. ”
These rules probably explain much of the assignment of collective uniform titles. Assign at first instance, and there can be different opinions concerning whether a title is “adequate”.