Why would data.loading not become true during data.fetchMore?

Question

Inside render:

  console.log('render', User.length, loading, networkStatus)

When I call data.fetchMore twice, I get:

render 100 false 7
render 200 false 7
render 300 false 7

Whereas I expect:

render 100 false 7
render 100 true 1
render 200 false 7
render 200 true 1
render 300 false 7

It works as expected (loading becomes true) in this example:

But not in my code:

File: