transform/vector lists & Vector3.Set issues

So i have problems using Vector3.Set, it does not seem to work when using any list.

what does work:

• Vector3.Set

• vectorlist[i] = vector

• transformlist[i].position = vector

what does not work:

• vectorlist[i].Set

• transformlist[i].position.Set

reading on the web i find it should not work with .position as this should be a copy not a reference, but this is false, (afaik..) as u can use it as transform.position = vector (this should not work with copy's).. so why does .Set not work...? a list should not return a copy (as we can prove this by setting the vector directly using transformlist[i].position = vector) also if it does not work because of .position.. why does directly setting a list of vectors not work either ( vectorlist[i].set )? any suggestions? i really feel like i should report this as a bug but maybe someone has some suggestions or knows what i am doing wrong.

.Set ONLY works when using a vector3 NOT from a list.

below is some code, supporting this is a scene with an empty game object (StartObject) with 20 cubes as child. pressing S and F changes the positions of the cube while A and D does not
(actually.. D it sets them back to the last value of F (not doing anything with vectorlist[i].set))

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class TESTSET : MonoBehaviour
 {
     List<Vector3> vectorlist = new List<Vector3>();
     List<Transform> transformlist = new List<Transform>();
 
     public GameObject StartObject;
 
     Vector3 tempvect;
     // Start is called before the first frame update
     void Start()
     {
         foreach (Transform child in StartObject.transform)
         {
             transformlist.Add(child);
         }
         Debug.Log(transformlist.Count);
 
         for (int i = 0; i < 20; i++)
         {
             vectorlist.Add(new Vector3(0, 0, 0));
         }
 
     }
 
     // Update is called once per frame
     void Update()
     {
         //DOES NOT WORK
         if (Input.GetKeyDown(KeyCode.A))
         {
             for (int i = 0; i < 20; i++)
             {
                 transformlist[i].position.Set(Random.Range(0, 10), Random.Range(0, 10), Random.Range(0, 10));
             }
         }
 
         //DOES WORK
         if (Input.GetKeyDown(KeyCode.S))
         {
             for (int i = 0; i < 20; i++)
             {
                 tempvect.Set(Random.Range(0, 10), Random.Range(0, 10), Random.Range(0, 10));
                 transformlist[i].position = tempvect;
             }
         }
 
         //DOES NOT WORK
         if (Input.GetKeyDown(KeyCode.D))
         {
             for (int i = 0; i < 20; i++)
             {
                 vectorlist[i].Set(Random.Range(0, 10), Random.Range(0, 10), Random.Range(0, 10));
                 transformlist[i].position = vectorlist[i];
             }
         }
 
         //WORKS AGAIN
         if (Input.GetKeyDown(KeyCode.F))
         {
             for (int i = 0; i < 20; i++)
             {
                 tempvect.Set(Random.Range(0, 10), Random.Range(0, 10), Random.Range(0, 10));
                 vectorlist[i] = tempvect;
                 transformlist[i].position = vectorlist[i];
             }
         }
     }
 }