If I clicked on that button and received that response, everything I could find connected with you and your domain would go on my blacklists. Misleading people is a poor way to build trust.
Your "I think it's much more likely" is a bit odd considering what you know about me (ie. almost nothing). "Outrage" is also pretty exaggerated. There are millions of commercial outfits out there in the world, the vast majority of which I'll never have anything to do with. There's a low bar for me to exclude just one more from consideration.
Now the dev can go build a working version putting in 200-500 hours into the MVP and find the next set of 20 people who are ready to use that software, with validation at hand.
However, I agree that better messaging can be used instead of straight up misleading people. Since if it does become widely practiced, people will generally become mistrustful (again, the odds of that happening is low).
~ 2 cents
I'm not denying that poor behaviour can net more customers -- on the contrary, it's by far the easiest way of doing so. My response was in the domain of ethical, not commercial, calculus.
I would have validated the viability at the cost of losing one customer. I think most would be willing to take that loss.