I can definitely take a phone, use it for a day, and come away with some conclusions. That said, I think it takes a lot longer than that to get to really understand a device, find out all that it has to offer, and really know what is going on.
I’ve made the decision not to keep a google pixel after one day of usage, I posted a post here about my experience, what I didn’t like. Same for a Nexus 6. I could have definitely spent more time with both phones and probably should have. In both cases, I ended up going back to my iPhone pretty quickly.
But for a tech journalist, I imagine the reviews would be a lot more interesting, refined if they had used the phone for a week instead of just one day.
Always figured they did that to wet the appetite of us consumers - and like other posters here said, Apple sure as heck won’t give a phone to someone who said something negative, so it has to be positive, right? 🙂