`set_global` for nested loops doesn't work how I expect

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Sorry, this seems to be more of a tera question. I noticed that set_global doesn’t seem to work as I would expect, when used in the context of nested for loops.

For example, consider a simple i, j nested for loop, where we’re creating a list for every i iteration, and then using set_global to concat to the list within the j iteration. Like this:

{% for i in  [1, 2, 3] %}
  {% set list = [] %}
  {% for j in  [4, 5, 6] %}
    {% set_global list = list | concat(with=j) %}  
  {% endfor %}    
  {{list}}
{% endfor %}

The output of {{list}} here is:

[] [] []

This isn’t really what I expect would happen at all. Is this a bug in tera or am I misunderstanding something?

If I move the creation of the list outside of both loops, it behaves as expected. For example:

{% set list = [] %}  
{% for i in  [1, 2, 3] %}  
  {% for j in  [4, 5, 6] %}
    {% set_global list = list | concat(with=j) %}  
  {% endfor %}    
  {{list}}
{% endfor %}

Results in:

[4, 5, 6] [4, 5, 6, 4, 5, 6] [4, 5, 6, 4, 5, 6, 4, 5, 6]

Thank you

P.S: There is a workaround, which is to declare the list outside of both loops, and then use set_global in the outer loop to make the list empty, and then update it within the inner loop. This achieves the same effect, but I was still surprised to see this and think that I have to be misunderstanding something. E.g.

{% set list = [] %}  
{% for i in  [1, 2, 3] %}
  {% set_global list = [] %}
  {% for j in  [4, 5, 6] %}
    {% set_global list = list | concat(with=j) %}  
  {% endfor %}      
  {{list}}
{% endfor %}

Makes:

[4, 5, 6] [4, 5, 6] [4, 5, 6]

Which is what I expect