Apparently the maintainer trusted the first-time contributor enough to propose tackling another bug.

There is no trust needed when asking someone to fix a bug. It’s not like the maintainer would lose anything if the contributor failed to fix the bug.

Besides, I think it is natural to want recognition when you do a lot of work for free. Many other people wouldn’t do this unpaid work at all; recognizing their contribution is the bare minimum of good manners. Even in a company where employees are paid for their work, it is customary to give credit to people who have helped you. Most people don’t like to work in places where they don’t feel appreciated, and that is also true in Open-Source.