Some people refer to the rotating structure as “the sprinkler”, but at any rate the question has some merit.
Generally the middle of the structure has small sprayers evenly spaced, and the end of the structure has what looks like a regular sprinkler on steroids. The large throw increases the effective diameter.
It’s a fair question, but the net would be that you use a slightly longer structure and get a rounded rectangle, where the rounded rectangle is just a truncated circle of the area the same sprinkler could cover in theory. Weigh that against the yield and extra maintenance costs.
I haven’t seen this many times, but the Wikipedia article points out there are linear systems that irrigate rectangular areas. They use a canal on one end and pumps on the rig. That explains an unanswered question about irrigation practices I’ve seen in Eastern Washington.
Most of the time the rows are circular the irrigation system is a moving structure that rotates around the central point, where water is pumped into the system, then drops down on the crops.
They frequently do have a sprayer at the end, but it's not sufficient to cover more than an extra few rows around the corners.
The machines often have a radius of 400m, so they're a lot bigger than the range even a firehose could achieve.