It doesn't work that way because discussing the latest update is a big part of being a fan. Imagine if the vast majority of the fans did actually wait to play the first half until the second half came out. The relative smattering of feedback would come across as a lukewarm response to the devs, who would probably kick themselves for releasing an inferior product most people refuse to play. Meanwhile if large numbers of fans play the update immediately, that's good for feedback, but not much fun for the holdouts who will never really participate in the feedback for that portion of the game. The only way to avoid the issue altogether is to release the update in one piece as originally intended, but then the people who just want something new to play are stuck in the doldrums and the devs are left chewing their nails. Someone's ox is going to get gored here, we just have to hope it's the smallest, least productive one. (And, you know, not mine!

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As far as the whole thing fitting together seamlessly once the second part is out, well, maybe. It really depends on how well the two halves stand on their own. Ideally you'd want each half to have a rising action/peak/falling action structure with a good variety of character moments and plenty of sex, which may or may not work out well depending on how TD was planning it. You can try to make the first half more setup to to the second half's payoff, but that can be tricky lest it just feel like a frustrating tease in the meantime (and there will be considerable meantime). Conversely, you can try to add more material to flesh out both halves, but then you need to make sure it doesn't feel repetitive or tedious when you play through it in one go.
It's a tough balancing act and - crucially - TD originally balanced it to be played in one sitting. If TD thinks it would be viable to split them then I trust his judgement, but if he likewise thinks it would be optimal to play it all at once then I trust that even more. Admittedly, I'm an easy sell since I dislike the idea of focusing even more on Kathleen's stage act, but I'd like to think I could still appreciate the problem even the second half was more to my liking.
On that we agree, but it seems clear they themselves are wrestling with what the best play is. We'll see what they decide; they still have a couple weeks to mull it over and see which option feels most comfortable.