We also have an increasingly large number of ways to engage in the hobby without being a measurable metric - not that we ever have had a large number of reliable metrics.
Entirely irrelevant. When we were at a restaurant after a Con and the waitress asked us what we did and responded to that with "Like Final Fantasy" - that's when the shift happened.
It's been a while and was pre Eternal September but the biggest complaint I remember was that the revised DMG, etc had only been out a couple of years before Second Edition and given that was in the height of the "hur hur T$R" grousing...
It also allows for textual clarification, presentation and style refreshes based on marketing data (these kids are all about the X now), or format changes, such as a Trade paperback format. Sometimes you just can't errata in a fix in a "reprint."
I think that ties strongly to how you are defining the movement vector and if the percentage of the existing base you hope to engage with would translate to a large enough set of sales to support the efforts to establish your product line vs how much you might get running in a solo space or...
This begs the question of the bard to first-born exchange rate. How are they evaluated quality (or lack of)? chronology? Pure quantity? The mind wobbles!
I don't disagree with that at all. I find it odd to define chronologically backward rather than forward. I don't know that I think it's fully wrong-headed or anything of that sort, but it feels weird.
I have always assumed a clause like this is more protection from parallel or ignorant duplicated develop that could happen than any realistic expectation WotC might intentionally reuse a DMsG product material.