I suspect Jim means the 1980s for getting the catalog material done farther in advance. In 1988, when I started with TSR, the company was already working with advance catalog copy and cover art. Editors and line heads had to provide summaries of content for each product, along with cover art orders, months ahead of time, frequently well before the books were written. (That's how you end up with the occasional cover-product mismatches, like Tantras, both novel and module. The Avatar covers were finished long before the novels and the modules.)
RPG Geek has entries for many of the TSR company catalogs from the late 80s and 90s here: https://rpggeek.com/rpgseries/19204/tsr-product-catalogues
Between 1988 and early 1994, when I stopped working with TSR, the overall movement had been to complete products earlier, for a variety of reasons (to provide near-finished books to fiction reviewers who wanted galleys six months before publication, to have more time to schedule for the best print costs, to increase overall schedule flexibility, and so on). By the mid-1990s, the company was completing RPG and fiction material farther ahead of ship date than they had in the late 1980s. And that meant an increase in the time gap between when the freelancers were being paid for a product and when the company brought in any money from that same product. (Random House typically paid TSR on ship.)
TSR's cash flow problems made themselves known outside the company by 1995 or early 1996, when the company started to pay bills late. By 1996, they had stopped paying me and many of the fiction authors the royalties that were due several times a year. They owed a long list of individual writers tens of thousands or hundreds of thousands of dollars. And that's just the debt for late/unpaid fiction royalties. Freelancer payments of other sorts had become routinely late, too. As we know now, TSR was in a financial tailspin.
If a dictate on the production schedule--shortening up the time between project completion and ship--came down from upper management, that would have been why. The completion–ship gap would have been one of the few areas where TSR could control the pace of the cash outlay for products. Shortening the gap to one month is ludicrous, of course, but it would not have been unusual for management to go completely overboard on such a dictate. That's just speculation, though. I was outside the company at that point and did not see that dictate play out firsthand.