AOC2024 Day 6 Clarification

Hey @jonathanpaulson thanks so much for posting your solutions to this year's Advent of Code. I especially liked your topological sorting solution from [Day 5](https://github.com/jonathanpaulson/AdventOfCode/blob/112541b3f31cef35b7d2346c0b9386eefc0ebd05/2024/5.py).

I'm just wondering about [Day 6](https://github.com/jonathanpaulson/AdventOfCode/blob/112541b3f31cef35b7d2346c0b9386eefc0ebd05/2024/6.py) and why is it that you loop over all of the map's cells and, each time, repeat the simulation process from the guard's starting point. I believe this is crucial to my understanding of part 2 of that day. Would appreciate your response.