Jeff Atwood's Mar. 19, 2010 SE post Should the weight of question upvotes be reduced? asked about reducing the question upvote reputation changes from +10 to +5, with some discussions there both for & against it. In particular, though, his blog post Important Reputation Rule Changes, also on Mar. 19, 2010, which describes the retroactive change, states 3 main reasons for this change:
While we value good questions (and asking a great question is absolutely an art), we want to explicitly encourage people to provide the best possible answers. Without people interested in providing good answers, the questions are moot. We know that answers have more intrinsic value than questions, and the reputation balance should reflect that.
The question asker already enjoys a substantial benefit beyond reputation gain from upvotes on their question — namely, they get great answers to their question! Thus, the asker shouldn’t need as much reputation gain.
There are a few users who ask hundreds, sometimes even thousands of questions. Over time, these users generate a fairly sizable reputation entirely through the tiny trickle of upvotes gained by these questions. In a sense, we want to discourage question asking a little bit, and make sure that people who ask questions are doing it for the right reasons and not to generate reputation.
Somewhat later, Jeff Atwood's June 11, 2011 blog post Optimizing For Pearls, Not Sand says
Incoming questions are a universal constant, all around us in countless billions. But answers — truly brilliant, amazing, correct answers — are as rare as pearls. Thus, questions are merely the sand that produces the pearl. If we have learned anything in the last three years, it is that you optimize for pearls, not sand.
That’s why we’re determined to keep question quality high, even at the cost of refusing a little sand. It’s true that you can’t have Q&A; without questions, but having the wrong sorts of questions is far more dangerous. The fastest way to kill any Q&A; site is to flood it with low-quality questions.
Now, Sara Chipps' Nov. 13, 2019 blog post We're Rewarding the Question Askers announcing the reverse change, i.e., question up votes are now retroactively going from +5 to +10, states
... Three years later, a decision was made to devalue upvote reputation on questions. The idea was that this change would encourage people to focus on providing good quality answers rather than asking questions.
We can look back on this decision with the benefit of hindsight. This decision may have been the right call then with the information we had at the time, but we have seen the effects it has had on our community. We reward people who give answers at a higher rate than people that ask questions.
I find it interesting, and rather telling, that nowhere later does it explicitly say anything about how the earlier change seemed to affect the number of questions asked, the quality of the questions or anything else like that. Also, it doesn't directly address, and in particular refute, any of those 3 points originally made by Jeff back in 2010 as to why the question up votes reputation change was being decreased then, nor his later post about how, although you want to keep question quality high, you especially want to encourage good answers. From my admittedly somewhat limited experience, especially compared to some longer term, more involved members, I believe those initial points still mostly apply today as well.
I think if you're going to reverse an earlier change, you should address the reasons for that previous change to indicate how they no longer sufficiently apply, or that other new reasons which counteract them are more important. Apart from Sara's brief statements about how we "can look back on this decision with the benefit of hindsight" and "we have seen the effects it has had on our community", is there any other discussion about this? In particular, is there any hard data to support that the earlier change was a mistake, or that this current change will overall improve the situation?
I believe the net effect of this change will be site-specific. My main concern is the change was made mainly to try to get more questions being asked (in particular, get more traffic to the sites), even though the overall quality of the questions may become somewhat worse on many sites, in particular the main one of Stack Overflow. Nonetheless, I hope I'm wrong and that things will generally work out better than before, or at least not any worse.
Update: The SO meta post What was the context of the decision to lower the value of upvotes to a question? asks a similar question to this one. There's currently one answer by Cody Gray which gives some of the background & reasoning. That is the sort of thing I'm asking for here. I hope we eventually get even more details here and/or in that other post.