I suspect the typical PE exam is quite a bit more rigorous than the typical technical interview. Technical software engineer interviewees are asked to do thinks like reverse linked lists and provide the most basic runtime and space complexity analysis. The structural engineering PE covers everything from load analysis and building codes to runoff analysis an slope stability[1]. There are 9 different "breadth" exam areas and 3 different "depth" areas, and they're all covered.
I think it's slightly ridiculous to compare understanding basic datastructures and algorithms to sitting for a PE.
[1] http://ncees.org/wp-content/uploads/Civ-Str-April-2015_with-...