> Thinking of food only on its nutritional aspects is reductive

A reductive approach seems to be the problem of artificial meat, in the first place.

> From a health point of view, fiber is a necessity

If there is a healthy microbiome to digest the fiber, you may want to feed that microbiome with fiber so it stays alive, and even improve the population that way. And I see that fiber can mitigate blood sugar spikes. However, fiber also takes up valuable minerals, prohibiting their uptake. I do not think that the situation is as clear cut as you present it.