Regarding the bolded text, that's exactly what it comes down to. Is it's user based experiences. No two forum members or any other iPhone owner will have the same battery life, because they use their iPhones for different purposes, which have an affect on the battery life with applications, signal strength, multitasking, etc.
Point is, is that you will read positive experiences and negative experiences, but that applies to any iPhone, not just the iPhone 7 Plus. It's really varies on how you use your iPhone more than what the actual numbers stated the iPhone can be rated for battery life.
That's the thing. It was the same user. The guy who wrote the iPhone 7 review on Techradar. He couldn't get through a day with the 7, but he was able to easily get through a day, even two, with the 7 Plus. I'm starting to think his 7 might have had a bug.