I think there's a connection here with the mythic 10x developer as well. Some developers are just so much slower at the Difficult Problems, so that the developers that are good at them seem like 10x (or 100x or infinitely) more productive than their peers. But I don't think they have the same leverage on the Hard Work problems.
And there are problems that are tedious because there's a huge amount of not very well organised data, and you have to go through it case by case.
Especially true if you're trying to fully internationalise something.
Examples: verifying international addresses, dealing with sales taxes in various countries and jurisdictions, dealing with import/export codes. Etc.
There's nothing conceptually hard about these problems. But a complete solution is just a very long list of nested ifs, and there's nothing much anyone can do about that. (Except buy/hire an existing solution - if someone else has done the work.)