Hi Kevin,
this is because you are updating the array itself instead of setting the value to a new array.
In no code/formula we are taking care for you to treat variable as immutable. If you are going to the js way, we need to be carefull about it
If you are not familiar with this synthax, we are just creating a new array and assign it to the var. When you do that, magic of Weweb can happen (always assign directly the value to the var)
This is also true for object, never update a subkey of a var, always create a new object.
If you want you can also use our safe formula method, even in JS