The principle that you should not reinvent the wheel (unless there's a good reason to) has not changed.

Code is a liability. Even if it is a small cost (in terms of time and money) at the time when code is generated, it can be a huge burden later, especially when you think about security vulnerabilities.

If this happened during my work, I would be very mad -- I would absolutely reuse an existing tool instead of expecting Claude Code to come up with its own half baked, bug ridden implementation of a common tool. Any (capable) human developer would have stopped and discussed with the team how to proceed.

In fact, I cannot tell how many times similar situations have happened where LLMs "made a decision" without consulting with me.