You are talking about submissive stuff and how DOM would not test it on him/herself. True. Your examples MAY be pleasent but ONLY for submissive or someone into specific kink, and, frankly, there's not so much people.
But edging machine is NOT necessary submissive. It may be used to enjoy a few minutes of intence pleasure whith a great orgasm in the end. And at the same time it will not demand any self control from a user. Edging is actually pleasent, for EVERYONE. That's why developers, even if they are dominant, can very well test it themself.
If I had to choose some SINGLE thing to pleasure mu cock, I would choose girl's pussy. But, luckyly, I don't have such restrictions, and may enjoy pussy, ass, mouth, hands (incl my own hands), vibrators, fleshlight toy.... And I'd also enjoy some male fucking machine or edging machine, I whould as well try e-stim if it's cost could not exceed my expectations of it... And I don't see why a developer wouldn't want to test PLEASURABLE device that he'd put so much effort into.Now i ask you what machine could suck better than a real mouth?