Yes. There won't be an open world to roam in RL and the reactivity of NPCs in the isekai will be limited.
My focus is on the main content and game completion before doing nice-to-haves.
Doesn't matter how many people say how easy it would be to add this one feature1 or that other feature2.
EDIT: If your comments have absolutely no relation to the game or me, and you don't even know the game, then I'm not entirely sure why you're posting your theory on game development processes in here. I don't think you understand the efforts required to add a full second world plus the reactivity for all the changes in relationships/appearance/lewdness/etc. the protagonist goes through.
EDIT2: Some further extension. You write that your arguments stand by their own merit, but in truth, there isn't even an argument.
Notice how you have used metrics such as x NPCs / afternoon+evening (???) which aren't metrics that can be used for any sort of discussion.
How much work goes into one NPC? How much into one corruption stage? The number of NPCs is a meaningless metric.
Your argument would look a lot better if you used something like #words, which isn't perfect either, but much better.
For some people an NPC may be a lewd NPC with a whole lewd scene attached and a reactive lewd NPC would be one with different lewd events at different corruption stages, but that's most likely not what you are talking about.
Here is how you can do an actual estimation to judge actual work load.
Let's say the NPCs in a game have a brief interaction of 100 words with the protagonist.
That's about 4 RPGM text boxes, 2 for the protagonist and 2 for the NPC.
There are 4 corruption stages, each with unique dialogue.
Then 30 NPCS would give 30 * 4 * 100 words = 12.000 words.
Let's say "one afternoon" and "one evening" correspond to 4h each.
Then, with these parameters, according to your thesis it would be simple enough to write (let's focus only on writing) 12000 words in 8h.
For reference, if you check the average writing speed per 8h work day, then you will find that it's at about 2000 words.
As another reference, 2000 words or 10k characters is a common length for japenese VN lewd scenes. So this is about the effort of 6 lewd scenes.
In other words, in this scenario with only a 100 words per NPC / corruption stage your estimate would be off by about a factor 6.
These are actually meaningful number with which you can work with because they eliminate invisible assumptions.
For example, if a single interaction is only 10 words, then the entire calculation changes massively.
And now it's no longer an act about talking about something "mystic" but a matter of talking about required workload vs expected return for the player.
For example, you could consider now the value of adding 6 lewd scenes vs adding these 30 reactive NPCs.
