Unit tests by a QA Engineer

Question

As I understood from some Q&A sessions (see this and this), unit tests should be written by developers.

At my previous workplace we tried to give this task to a QA Engine

Answer 1

A Developer or a fellow developer (code reviewer) should document the Unit test cases which in a way should be based on the Code developed or the Technical Design. However, a QA test cases should be written by the functionl testers that should be based on Functional Design.

The fundamental difference here is that the UT covers logic, internal flow, performance, optimization whereas the QA covers the functional flow to mimick user experience.