Garland uses $vars instead of $variables

you mean like this?

Maybe this is a good change, if only to be consistent with the other core themes. Not really seeing the bug here though, isn't it more of a task?

All $vars were converted to $variables in d8 #1963942: Change all instances of $vars to $variables, so this is a d7 only issue.

Patch no longer applies.

Patch does not fix garland_preprocess_node() or garland_preprocess_comment().

Review bonus #2094585: [policy, no patch] Core review bonus for #1987410: [meta] system.module - Convert theme_ functions to Twig.

Patch applies and works

Manual Review

Individual user account
Yes: Follows the guidelines for individual user accounts.
No duplication
Yes: Does not cause module duplication and/or fragmentation.
Licensing
Yes: Follows the licensing requirements.
Code long/complex enough for review
Yes: Follows the guidelines for project length and complexity.
Secure code
Yes: Meets the security requirements.

Committed to 7.x - thanks!