They thought it worked up to 1m token window

why would they think that? I'm not a pro, but I know you can't serve more than kv cache pool that you have. If you want to run concurrent requests, you need to have more kv cache pool than your context window. The entire thing is weird, my bet is they were thinking most people will be using about 100k cache, compacting, etc and not nearing 600k ever.