Were you looking for testimonials embedded in the essay to meet your expectations?
Of course, this wouldn't be acceptable as it would turn the piece unmistakably into a sales pitch for his product cementing your suspicions about the nature or motives behind authoring this post, a viewpoint which by the way I don't necessarily share.
This type of reporting that you're specifically looking for is best served with other formats like featured stories or in-depth analyses done by news organization; where they get to interview YC partners, alumni and startup founders, and solicit their opinions and thoughts about their experience with the organization, but even this reporting needs to be balanced and informative otherwise it will be mistaken for an advertorial or, as you guessed, a sales pitch.