1I and 2I look like chance. Loeb et al. put 3I's planetary passes at 1 in 20,000. Scored against all eight planets and random arrivals of its speed, it's about 1 in 300. I don't know how much more easily surveys spot objects along the ecliptic, which would explain some of 3I's coincidence.
I welcome forking the project and adjusting the assumptions I made, like a Bracewell or von Neumann probe would take a traveling salesman path, or that it would need to fly near multiple planets.