Just saying what? ...That this stress is comparable to that and inconsequential in the end?
If the asshats in the boat had instead observed the moose from a distance, and then later this moose had been surrounded by wolves it would be dead from the encounter with the wolves. That would be natural predation. If this moose ends up surrounded by wolves because of the stress of this event it will be dead. That would be unnatural predation that could be correlated back to its harassment by the boatload of jackholes.
What if this was a different scenario? Let's say you're out on a multi-day hike-in hunt. You're setting up camp for the evening when a pack of seventeen wolves surrounds your camp and moves in. It happens so fast and silently you're surrounded before you can prepare or get up a tree. (You're probably saying, "That's impossible! Wolves don't move like that," but I bet the moose thought its encounter with the boat was unlikely too.) So, maybe you've got time to grab your rifle, load it, and take out a few dogs. Sh*t, you're empty... you see a gap, drop your gun and you run. The wolves chase you through the bush, for fifteen minutes. You're running for your life, over logs, headlong through bushes, knowing you're about to feel the bite on your Achilles tendon that brings you down. You're gasping for oxygen, ignoring the scratches all over your face and arms, in complete panic because you know the game is up.
And then you stop because you realize all you hear is silence behind you. They're gone. You can't explain why, but they're gone. Maybe your flight through the bush startled a deer and they switched targets. Who knows, but thank the FSM you got away. You circle back to get to your gun, pack up and get the hell out of dodge. (At the very least you need new pants.) As you're creeping back you're listening oh-so-carefully for a bark or a howl, any noise from those wolves... that in the dark you don't see the 190-lb cougar crouched in the brush at the side of the trail before it launches. Did the wolves kill you? Nope. Can their actions be correlated to your untimely demise? Yep.
Of course that's not a likely story. But neither is a bunch of citiots in a jetboat chasing a very undomesticated moose for fifteen minutes and then letting it go for no reason. For every second of them chasing that moose, it was running for its life. And for a good, long while after they finally let it go it was very vulnerable.