The rule
Navital Labs doesn't market its software so much as document it. The tone is meant to be observational rather than persuasive: describe what the thing does, specifically, and let the reader draw their own conclusion about whether it's good.
The practical version of the rule is a single sentence — never describe a product by its implementation, describe what changes for the user. Nearly every piece of writing here has been rewritten at least once because of it.
Why it holds up
Specific writing is easier to trust and harder to fake. A sentence describing exactly what happens when someone clicks a button can be checked. A sentence describing how powerful something is cannot, and readers know this, which is why the second kind slides past without landing.
There's a design version of the same idea. An interface that states things plainly — clear labels, honest empty states, error messages that say what went wrong — reads as more trustworthy than one that's been styled to look confident. The register is the same in both cases.
What it costs
It's slower. A specific sentence requires knowing the specific thing, which sometimes means going to check before writing a line. And the writing is quieter than the alternative, which means it does less work in contexts that reward volume and confidence.
We think that trade is right for a company whose products people have to rely on for their actual work. It would probably be the wrong trade for something bought on impulse.