Every bug stems from a line of code. Every line of code is written deliberately by a programmer. Therefore, every bug is created deliberately by a programmer.
A programmer must not write buggy code.
Sporadic unexpected features are intrinsic to buglessly developed projects.
Tested code can only pass the test. Untested code can do anything.
No bugs means no tests required.
What you think is a bug is not a bug. It is an opportunity for a feature.
Do not git blame.