@Averhoes Yeah, means, its all speculation and assumption but casting Nell fisher, isnt she like important? i dont know about US actors. Also who's vanishing can be more terryfing than a child. Also we see her involved more with Henry and see her screaming or paniking.
Unless they wanted to do "The Vanishing of Will Byers- Part 2/Unsolved Connection"
Also S4 had some major leaks weeks before it release.