Backpressure - Controllable RxJS Producer

backpressure.js

const rx = require('rx')

let s = new rx.Observable.from([1,2,3,4,5,6,7,8,9])
let ss = s.controlled()

ss.subscribe((x) => {
  console.log("Pull "+x)
  setTimeout(() => process(1, x), 100)
})

function process(i, x) {
  if(i == 3) {
    ss.request(1)
    return
  }
  console.log('Process ${i} - ${x}')
  setTimeout(() => process(i + 1, x), 100)
}

ss.request(1)

backpressure2.js

const rx = require('rx')

let s = new rx.Subject()
let ss = s.controlled()

ss.subscribe((x) => {
  console.log("Pull "+x)
  setTimeout(() => process(1, x), 100)
})

function process(i, x) {
  if(i == 3) {
    ss.request(1)
    return
  }
  console.log(`Process ${i} - ${x}`)
  setTimeout(() => process(i + 1, x), 100)
}

for(let i = 0; i < 100000; i++) {
  s.onNext(i)
}

ss.request(1)

Why pausable() not work?