Absolutely, yes! Then make it two or three people, maybe 10 and there are still n-times too many people working on flutter compared to cURL.
Which boils down to: Number of devs vs. people using something is a very bad metric. Even number of supported devices won't work good in this case (I assume cURL runs basically everywhere).
I think it's very difficult to estimate complexity, and then make a statement about "how many people are enough" is even more difficult. Some environments are harder and more complex, some are just very heterogen and some are both. Sometimes it's the organizational overhead, maybe even something else.
Suppose Flutter may be an order or two magnitude more complex than cURL.