AsyncOperation activating immediately even with async.allowSceneActivation = false;

Hi. Here is my code. I am trying to load another scene in the background (hence the low background loading priority to keep the gameplay uninterrupted.) However it loads the destination scene as soon as I load the first scene IN BUILDS ONLY. The editor has a temporary lag instead with makes no sense because the thread is supposed to be low priority but whatever; if it works in the build I'm happy. But it doesn't because it loads the other scene instantly. Any idea why?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class asyncLevelLoader : MonoBehaviour {
 
     public AsyncOperation async;
     public string sceneToLoad;
 
     public bool loadIntoRam = true;
     public bool loadScene = false;
 
     void Awake(){
         Application.backgroundLoadingPriority = ThreadPriority.Low;
     }
 
 
     void Update(){
         if (loadIntoRam) {
             loadIntoRam = false;
             if (async == null) {
                 LoadIntoRam ();
             }
         }
         if (loadScene) {
             loadScene = false;
             LoadScene ();
         }
     }
 
     public void LoadIntoRam(){
         async = Application.LoadLevelAsync (sceneToLoad);
         async.allowSceneActivation = false;
     }
 
     public void LoadScene(){
         async.allowSceneActivation = true;
     }
 
 }