Nobody has said it is. That doesn't stop them from using Lian Li's distribution network - LL just likely acts as an intermediary in the process in terms of getting distributors on board etc. Given how conservative distributors tend to be it's no mean feat to get them to agree to distribution of such a niche case at all - they'd much rather distribute yet another yawn-worthy high margin rgb-laden mid-tower, because they "know it will sell" (even if the reality is that distributors constantly make bad bets on "safe" products).They said its not a lian li case
That being said, all volume from the first two batches is no doubt already sold to various distributors. To free up some of that for direct sales (disregarding whether that might be contrary to the terms of the distribution contracts, most of which no doubt contain some sort of "don't screw us over by going around us and selling the product yourself to our region") they would need to be 100% sure they could make up that volume in production before the ship date for that batch, which I'm guessing would require it to have been planned months ago. Factories are not set up for rapid change, and running a new batch of a case that isn't even on the market yet is likely not high up their list of priorities. They also no doubt need to produce a pretty significant amount for another batch to be feasible, potentially leaving them with inventory sitting unsold - another thing a new business really should avoid. Unsold inventory is lost money (interest on the loans needed to pay for materials, parts, labor and production) after all. The longer it sits, the more expensive it gets, and the more unlikely the prospect of mass-market premium SFF cases becomes. Waiting it out is a much better long term strategy.
As for booking a new ship, remember that there are huge global shipping delays these days. I wouldn't be surprised if the lead time on any shop freight at all is several months at the least. There's definitely no way they can just go out and book room for a new container on a ship in any given date. (There's also a global shipping container shortage, just to make this extra fun.)