You're missing the point. Why is there a 3+ week pre-announcement for such a minor higher bin?
Why not? It lets people know that a new product is coming, so if someone is planning to build a new PC soon, they can decide whether to hold off a bit if they are willing to spend more for a little more performance. It's in AMD's best interest to let people know ahead of time that a new product is coming.
And again, we don't actually know how much of a "minor improvement" it might be, at least until they have been benchmarked, since no information about multi-core boost clocks has been provided. And even for lightly-threaded workloads, it's possible that the chip might do a better job maintaining those maximum boost clocks more consistently.
If you really want an example of a company announcing a minor update way too early, Intel announced the 9900KS in May of 2019, but didn't actually release it until the end of October, over 5 months later. And it was similarly just a better binned 9900K with a bit higher clocks, launching a year after the original version of the processor, at a higher price point. Three weeks is far more reasonable than 5 months.
So while being a better bin, it also wasn't the exact same die as the 9900k which is likely to be the case with these AMD CPU's.
Not true. Intel had apparently already added those mitigations to newer versions of their existing processors, but Tom's Hardware mentioned they were testing the 9900KS against an earlier version of the 9900K. It sounds like Intel switched to that newer stepping for their 9th-gen processors about half a year prior, around the time they announced the 9900KS.
As for base clocks, those don't really matter much, especially since motherboard manufacturers tend to ignore them in their default configurations. The base clock will typically only matter in the event that the processor is throttling. So, ultimately the 9900KS is just a better binned 9900K with the same boost clocks for lightly-threaded workloads on 1-2 cores, 200MHz higher clocks for 3-4 cores, and 300MHz higher clocks for 5+ core workloads. Overclocked, there's maybe a few percent performance difference between them on average. It's fine that they released such a processor, but it's similar to what we are seeing with these XT parts, albeit with a much longer time between the product's announcement and it release.