I get annoyed by people crossing in the middle of a block rather than walking down to the nearest intersection*. But it sounds like this person was crossing at an intersection, but took a slightly more direct path to where they were going rather than staying in between the white lines the entire time they were in the street. And you’re annoyed because they didn’t stay in between the white lines. I don’t see what the big deal is. They crossed at an intersection. What does it matter if they’re physically in between the lines that mark the crosswalk, or a few feet outside of them?
In my neighborhood there’s a four way stop at nearly every intersection. When I moved there over a decade ago there were no actual crosswalk markings at any of these intersections, but like someone said upthread in California (and I assume most other states) every intersection is considered a crosswalk even if there aren’t actual lines painted on the pavement. But earlier this year for some reason the city went and painted crosswalk markings at every intersection. Except the crosswalks they panted don’t line up with the sidewalks (they do line up with the curb cuts, which I assume is why they put them where they did). I think it’s silly to walk three feet to my right, cross the street, and then three feet back to my left to get back to the sidewalk, just because that’s where the magic white lines are. So I don’t. I just keep walking in a straight line and cross about three feet away from the marked crosswalk. Oh no! I’m outside the crosswalk! Lock me up!
*If it’s a busy street. I don’t really see any harm in crossing a residental street with no traffic where ever it’s convenient.