Why is a tooltip ignoring a Rect and not another?

Hi, I didn't figure out how to write a good title, sorry.

I'm trying to make a grid of buttons to appear as an inventory. I'm totally new at Unity, please excuse my ignorance..

I'm rendering the inventory on the OnGUI event, I specify the position and size of the inventory area, and then I specify a portion of it to an area called tooltipArea. I want to hover a button and a tooltip that appears on the bottom part of the inventory (in the tooltipArea), with some characteristics of the item hovered.

What I did is that I assigned the tooltip to a button succesfully, but this tooltip won't appear if it's outside of the button area.

This is a screenshot of what I have:

And this is my code:

 void OnGUI(){
         GUI.skin = inventorySkin;        
         if(isMenuOpen){
 //These boxes are for seeing what space are this areas actually occupying
             GUI.Box(new Rect(inventoryAreaNormalized.x - inventoryBackPadding, inventoryAreaNormalized.y - inventoryBackPadding, inventoryAreaNormalized.width + inventoryBackPadding*2, inventoryAreaNormalized.height + inventoryBackPadding),"");
             GUI.Box(new Rect(tooltipArea),"");
             GUI.BeginGroup(inventoryAreaNormalized);            
             int count = 0;

 //My intent of grid...
         
             for(int renglon = 0; renglon < nrenglones; renglon++){
                 var top = renglon * baseItemArea.height;
                 for(int columna = 0; columna < colSize ; columna++){
                     var left = columna * baseItemArea.width;
                     var thisRect = new Rect(left, top, baseItemArea.width, baseItemArea.height);    
                     
                     if(Inventory.ItemBag.Count > count){                        
                         if(GUI.Button(new Rect(thisRect), new GUIContent(Inventory.ItemBag[count].Quantity.ToString(), Inventory.ItemBag[count].Icon, Inventory.ItemBag[count].Name))){                            
                             //Some actions
                         }

                         //THIS DOES NOT WORK
                         if (!string.IsNullOrEmpty(GUI.tooltip))   
                             GUI.Box (new Rect(tooltipArea), GUI.tooltip);
                         
                         count++;
                     }else if(renglon * colSize + columna + 1 <= Inventory.Capacity){ 
                         if(GUI.Button(new Rect(thisRect), "")){    }                                            
                     }else{  items
                         GUI.Box(new Rect(thisRect),"");
                     }
                 }                
             }        
         GUI.EndGroup();
         }
     }

Ok, so please, any guidance is very welcome, I'm just playing around and I can't figure this out, I searched in the questions in this forum and I didn't got this particular question.

Again, to clarify, this line:

 GUI.Box (new Rect(tooltipArea), GUI.tooltip);

only works like this

 GUI.Box (new Rect(thisRect), GUI.tooltip);

placing the tooltip over the button (an undesired effect).

---

Edit:

So I changed

 GUI.Box (
     new Rect(thisRect.x+15,
             thisRect.y+15,
             thisRect.width,
             thisRect.height), GUI.tooltip);

just to see if it had something to do with the button area, but no. This is the result:

Why is the tooltip ignoring the tooltipArea? What am I missing?