Knowing your audience seems really important to this discussion. Those of us with technical knowledge immediately want to know "what does it actually do?"
But there are a lot of decision-makers without technical knowledge who might be swayed by their "general impression of the people they meet." This group doesn't necessarily care if they're in need of what you're selling.
There's a spectrum between these two extremes and how you approach marketing is going to depend on your opinion of how the audience is distributed in this spectrum. If you believe there are more people toward the latter end of the spectrum then a more general, details-free approach may make sense.
I think it's a joke, but there is actually real advice along the same lines. When cold emailing someone with the goal of getting a phone call, you want to avoid giving the person enough information to say no.
I won't pretend I'm great at sales, but this is directly contrary to the advice I get, which is you want to filter out people who are a sure "no" or not a match (eg, on budget) as fast as possible so you don't waste sales resources on them while minimizing the chance of leaving a bad impression from trying pressure tactics on someone who wont buy.
What am I missing? (I guess it could be intending to be unethical, but I prefer to assume I don't understand.)
This, so very much this. I love what Jeff Thull says about this... "always be leaving" (as opposed to "always be closing"). Make it clear to the prospect that you are not going to be the stereotypical sales-person who grabs onto them like a little pit-bull grabbing onto your leg, and who won't let go until they've been beaten over the head with a stick. Show them that you respect them, and leave as soon as it's clear that there isn't a good fit. Leave a good impression and later, when they do need your "thing" they're more likely to call you up (or take your call when you call again in a year).
If you leave a good impression, there's every chance they'll recommend you to someone who does need $thing, doing much of your selling for you -- you just have to leave them thinking "well, $thing wasn't right for me, but I'd do business with $person and $company".
Why? What's the point in wasting time having a call with somebody when the answer is going to be "no" either way? Better to get to "no" as fast as you can, so you can move on to a better prospect.
No one is ever going to say 'yes' to a $10M sale from a cold email. They'll only say yes after they've met you in person, but they're not going to agree to meet you in person until you've done a phone call.
The problem is that everyone will say they don't need what you're selling, even if they do. You want to disqualify folks as fast as possible, but email doesn't work for that because even if you're selling the cure to cancer to someone with cancer, you're still going to have basically a 100% false negative rate.