Gitlab-CI keyword `rules:changes` cannot evaluate nested variables

Summary

Gitlab-CI does not seem to evaluate nested variables with depth > 1 in the rules:changes keyword.

Steps to reproduce

1. Declare a CI with a job
2. Add one CI/CD variable based on other CI/CD variables
3. add rules:changes conditions based on the indirect CI/CD variable
4. The condition is not met when the file is modified

Example Project

I've shown the bug in this project In here, we can observe that job_explicit and job_implicit_level_1 were triggered:

# job_explicit
# [...]
    rules:
        - changes:
            - "foo"


# job_implicit_level_1
# [...]
    rules:
        - changes:
            - "$DIRECT_VARIABLE"

Where DIRECT_VARIABLE is a variable assigned to a string directly (foo), but job_implicit_level_2 is not triggered, although its value should also be foo

# job_implicit_level_2
# [...]
    rules:
        - changes:
            - "$INDIRECT_VARIABLE"

(The only difference is that INDIRECT_VARIABLE is assigned to DIRECT_VARIABLE, which is thena assigned to foo.

If I run the CI manually (and all 3 jobs run), we can see that all 3 jobs can output both of the variables in their script

What is the current bug behavior?

rules:changes does not evaluate correctly variables that contain other variables.

What is the expected correct behavior?

rules:changes should evaluate variables even if they are defined based on other variables.

Output of checks

This happens on gitlab.com. and hosted instances

Results of GitLab environment info

This result also happens on hosted instances (I'm using 13.9.3 (ea359c58edb))