It's just so obviously an absurd statement to say that if a bug is fixed and not documented meticulously in JIRA it is as useless as if it was never fixed at all. A huge portion of the day to day work of software engineering happens without explicit documentation of every decision for every change for every line of code. Life continues, software is built.

The necessity for documentation exists along a spectrum, and the means of documenting things exists along a spectrum. We have lots of tools for documentation. Design docs, commit messages, the commits themselves, JIRA, email, chat. Which one is appropriate depends on the given situation.