Anyone with eyes wide open cannot help but being drawn into this mystery.
The core of the mystery around Vermeer is that, as the movie captures, his paintings are like Ektachrome slides. Perfect in their fidelity down to details not otherwise discernible by the unaided eye.
How could Vermeer have accomplished that?
I agree that the experiment of reproducing a Vermeer with optical tools had some elements that prevent it from being absolutely the answer to how Vermeer created his paintings.
But the experiment AND a lot of other evidence makes it extremely unlikely that Vermeer just lifted his paint brush and "painted what he saw."
This effort, though not conclusive, is a major contribution to art history.