Is PostgreSQL a serious product? For me the answer is "NO". A product with a bug that last for years and the community knows.
It is not serious.
If you are trying to be a troll just go away, we don't need that here. If you are just venting consider that this project is no more or less likely to have oversights, incomplete documentation, or a myriad of other human induced issues than any other.
Reading the linked bug report the conclusion was "won't fix - at least not right now". Sure, it probably should have been documented but wasn't. It happens. And given the lack of complaints in the intervening years the decision, to not devote volunteer resources to a marginal feature, seems like the right one. Your active recourse at this point is to either convince a volunteer hacker to take up the cause - which your attitude doesn't help - or pay someone to do it. Or figure out a personal work-around to live with the current reality. Given that there is ongoing discussion as a result of your report (i.e., the report has merit regardless of how it was reported) means you should either meaningfully contribute to the discussion or shut up until they are done - at which point you are back to making a decision. Prompting politely for attention if the thread seems to languish without a clear resolution is, IMO, acceptable.