Because it's intentionally ambiguous in the film
Galadriel only says "he", not "Boromir".
Does Boromir want it? Sure, we've seen that when the Ring "falls" into the snow in the Misty Mountains.
How about Aragorn though? The reason the scene with Frodo and Aragorn at the Breaking of the Fellowship is so powerful is because up to that point we don't know. Up to that point, Boromir has always been the one who's been closer to the hobbits (especially Merry and Pippin), and Aragorn has been quite standoffish with them. He's been a good leader, but not necessarily likeable. We also know that Aragorn is afraid he'll be tempted the same way his great-however-many-grandfather was - so not only do we not know, but the character doesn't know either.
The story of the Fellowship film isn't just character development for the hobbits. Jackson also managed to build in character development for Aragorn, Legolas and Gimli, something which is famously absent from the book. Remember that the book itself was a loving pastiche of Norse sagas. Jackson knew that he had to produce something which would stand up to modern standards of story-telling. Aragorn facing down that temptation is the point where he rises to be better than Isildur. Everything afterwards is detail - exciting detail, to be sure, but closing Frodo's hand back over the Ring is when he earns the right to be king, and Boromir says as much as he dies.
And the "he" could also be Sam, or even Merry or Pippin. Frodo is already getting the effects of the Ring by that point. Pippin proves his own weakness later with the palantir, after all. Sam has to virtually drown to prove himself to Frodo.
There's no shortage of "he"s, basically.