Blue
Ravenous Bugblatter Beast of Traal
Except for the evidence I provided immediately after saying it was patently obvious, you mean?
Thank you for your participation.
I have to admit I what I saw was evidence that particular settings deal with their mythos. Which is something that, as part of the cultures in the setting, is appropriate for a setting.
Can you give examples from the rules? PHB and DMG.
The PHB Appendix B seems to be in support of your argument, but it's an appendix for reference and not the main rules.
The DMG has an entire chapter on making your own multiverse, it does not require including any setting. (And if you do, it explicitly calls out that they are yours and may differ from the published setting which means it may not contain the Wall of Faithlessness, pantheons, or anything else of that nature.)