In general in PLs this is not true—the standard library is usually very carefully designed and all of its interactions are well-considered—but Python's libraries do seem to be more independently-updated than most.

Even so, isn't that an argument for a smaller, integrated team for the framework, rather than a large one made of ~1000 volunteers? A tightly-knit framework is much more likely to suffer from too many chefs than a disparate collection of library functions.

Between the parallelization problems inherent in a tight framework and the fact that its total surface area is also smaller than a PL that's maintained by about the same number of people, it sure doesn't sound like Flutter's problem lies in developer headcount.