@arashikitsu Not sure if you've made pasta before, but it's somewhat similar to that. A good Udon noodles depends not just on the type of flour and grind but also the temperature of the water. Ambient humidity affects moisture absorption, and it's very easy to over-knead which leads to a chewy noodle. And as you've said, adequate time to rest the gluten.
If you look at an Udon noodles recipe or tutorial, it's actually quite simple. But there's a reason why it's practically an art form in Japan.
Sure it's not difficult to make a noodle, but it's hard to make a noodle good enough to convince a team of chefs that this new cuisine is better than their native cuisine.
As for the broth, one made from dried seasoned meat (whatever they had lying around) wouldn't taste anything like Dashi. You can't even compare it to regular stock and in that much water it would be almost tasteless. Western broths often rely on fresh veg, herbs and some animal carcass, but Dashi requires very particular ingredients. Part of the umami comes from katsuobushi which takes up to half a year to prepare. It's also why Dashi tastes extremely different from western-style broths.
I doubt what they made tasted good at all, tbh. Though I don't remember the chapter too well. Not sure if you can tell, but I've pretty much given up making Udon lmao. I just go out and buy it now. Hahaha /endrant