That's exactly what parent post is saying I believe, the conversion rate is huge, clearly, but it can't be sustainable. The point is, that even a small fraction of advertising will be moved over to this cold-DM strategy, the funnel will collapse to the usual rates as soon as people catch on, same as every other "trick". Now, whether there's enough time between today and that hypothetical point in the future to extract profit using it, that's the real question here. I fathom there is, at least for someone, until trust is thoroughly destroyed. Repeat ad nauseum as trust moves and gets expended over and over, until possibly when no one trusts anything on the internet (or really any other theoretical platform with cheap global reach) ever again.
I also wanted to point out, the big 10% rate they're seeing is not for actual conversions, but replies, which are likely correlated, but a reply does not a conversion make. The real rate is presumably lower.