Here's what happens when a manager tries to fill tickets himself: his sense of control of the project is derived not from relationships of trust and cooperation with his reports, but from direct involvement in the code. So naturally, any challenging or critical piece of code ends up getting written by him (because otherwise, how could he be confident about it?)
The manager is essentially holding two jobs at once so they end up working late or being overly stressed at work.
The devs will feel intimidated to make architecture decisions, because they know if they do something their manager doesn't like, it will get refactored.
They will also feel as if they are only given the "grunt work" as all the challenging work is taken on by their manager.
The code itself is in a constant state of instability because there is a tension between the manager needing the other employees' help to get the code written on time, while also needing to have that complete control and mastery over the code that can only come from writing it yourself. So people's work gets overwritten continually.
This is very bad and it's very common - managers should learn to delegate as that is an essential part of their job. If they can't delegate they should remain as an individual contributor and not move into management.