That's how the pilots do it, no point in turning early because while the large vessel perceives that there is risk of collision. the small vessel does not.
The other issue is while large vessel maneuver with a plan in mind the small vessels are using trail and error.
Last time I was inbound Puget Sound just after coming around Pt. Wilson we had small high speed cruiser on our port bow, steering as if planning to pass ahead but on collision course. The cruiser held on till he must have realized he couldn't make it then he turned to stbd to go astern.
The boat operator must have then thought going astern was going to take too long, so he turned to port to go ahead again but this time with course more to the left then original. But after he turned to port he was much closer, inside a mile but he must have realized for the second time he wasn't going to make it and turned to stbd a final time and crossed astern.
That's a typical encounter, one of many. The small boat operators don't understand the value of making a single course change for collision avoidance then holding that till clear. Instead they zigzag, oblivious of how that appears to the other vessel.
The boat operator was probably enjoying his day, out on the water, having a beer, enjoying some music, while on the ship it's looking like an in extremis maneuver might be in our very near future. The boat operators don't think in terms of "risk of collision", they're just zigzagging through traffic, on their way to wherever they might be going.