Full disclosure, I'm a YC alum whose last start-up was acquired by Google, who applied to this batch and didn't get an interview. YC is not the stamp of quality it once was, to be sure, though it still works as social proof, because investors (especially VCs) want to invest in companies other investors like (or failing that, companies they imagine other investors would like). YC would say that they aren't trying to b…
Imagine you ran a startup accelerator that didn't invest in a particular business model or product, but instead invested in a team of founders you thought had the potential to produce something great, even if it takes a few pivots.
Now imagine you didn't want to invest in a given company. Would your rejection letter say you disliked the founders, as people?
Of course not, you want to be on friendly terms, just in case. Far safer to just be "unconvinced" about their "product strategy" in its "current form".