I don't know what "field research" you have done, but I do know that if you look up hibernation on the internet or read books on reptiles, and if you talk to longtime tortoise keepers (which I have done many times,) you will find the vast majority of opinions on hibernation is that it is necessary for long-term health. Highgfield is a world-known tortoise expert who has studied these animals for decades. He says he has found that they do indeed develope health problems if they are not allowed to hibernate for a few years. He and plenty of other experts will site liver and thyroid damage, immune system suppression, and of course reproduction difficulties. These conditions may take years to develope, but they usually do eventually. Where do these beliefs come from? I doubt it is all just made up. What reason would someone have to make it up? I'm sure there are people who will say their tortoises are doing just fine without hibernation, but what we are talking about here is the preponderance of evidence and it seems to point to a true biological need for hibernation.
The fact that some tortoises die in hibernation is irrelevant to whether it is necessary for them or not. Women die during childbirth. People choke to death on food. Does this mean those things are not necessary? Just because some people don't know how to hibernate their animals properly does not mean everyone should just skip it out of fear. Knowledge is not that hard to come by concerning this subject, even though it is controversial.
You talk about "scientific proof." That is hard to come by on this subject because of the length of time it takes for health proplems to manifest themselves. We mainly have anecdotal and circumstantial evidence. But we have a LOT of anecdotal and circumstantial evidence and that can be very, very telling. Do you believe that smoking greatly increases your chances of getting lung cancer? Did you know that the evidence for that is only anecdotal and circumstantial? There is really no absolute "scientific proof" that cigarettes cause lung cancer; or that obesity will cause heart problems, for that matter. Yet both of these beliefs are accepted by any reasonable person. It is all just looking at the backgroud of people who get those disease and making the connection. Just like with tortoises and hibernation.