"so why not just strap a smartphone-shaped DSLR to the top of your computer monitor"
Because the concept of a DSLR makes absolutely no mechanical sense on a camera without a viewfinder.
"mirrorless 7.8mm 4K Sony sensor"
See, so it's not a DSLR, because its mirrorless... Although every webcam is mirrorless.
Does this webcam use interchangeable lenses, or what? Because the best I can tell this webcam is just an ordinary webcam, with the same tiny webcam-sized sensor. All they've brought to the table is the hack-fraud marketing and insane overpricing that one would expect from "former Apple, Beats and Uber employees".
Seriously, their marketing is so wanky that it must be sarcastic.
Opal themselves claim "DSLR technology on a webcam for the first time", but make no real attempt to explain what that means... Unless they legitimately believe a glass lens counts as "DSLR technology". Two paragraphs later, they call it a "mirrorless miracle".