That's kind of like catching an error and saying a year later "I meant to do it that way."
Leaving something open-ended is fine, but a good writer should acknowledge that in the text, provide some suggestions, call the DM's attention to areas that should be developed. Otherwise, it's just more plot holes and issues that a DM has to juggle along with table dynamics, rules, linking together 300 pages of plot, etc.
More likely, it's been written by committee and someone didn't catch it. It's not a feature, it's not even a bug, it's an ankheg.