It's a bit more complex than that.
T1 and T2 are essentially completely different conditions. Very simply, T1 is an auto-immune disease where the body does not produce insulin, or not in anything like sufficient quantities. T2s typically have plenty of insulin, but it's ineffective. There's a shared symptom - high blood glucose - but otherwise not a great deal of crossover. I wouldn't really start comparing T1 with pre-diabetes. It's a bit like saying floods and droughts are the same thing, because it's all to do with water.
There's a lot of confusion partly because up to around 20 or so years ago diabetes was thought to be a single disease with people "progressing" from not being insulin dependent to being insulin dependent. T2 as a concept didn't really figure - I have textbooks published in the late 1990s that were still taking this approach. That has changed a lot since, but you'll still read stuff on the internet that takes this line.
Pre-diabetic as an idea was developed only about ten to fifteen years ago to cover the fact that people's blood glucose was often no longer in normal range (almost all non-diabetic people fall somewhere between 35 and 41 on HbA1c) but not yet at the level where T2 would automatically be diagnosed. I had a full and painful range of diabetic symptoms with HbA1cs of 43 and 44 upwards, so I'm inclined to think that when I go out of normal levels, I have a problem, and I'm not "pre-" anything.
As T2s we have a problem dealing with glucose, resulting in high levels of glucose throughout the body, not just in blood. Our insulin response systems cannot cope. This results in both chronically raised blood glucose and raised insulin levels, probably weight gain, and a raft of other possible symptoms. But - there are lean T2s, and people's experiences can be very different. Some of us think there may be a number of T2 variants.
By "chronically raised" I don't mean the normal temporary rises and falls after eating. I mean long-term elevated levels that never really come down. These can result in physical damage, mainly to nerves and capillaries.
As with any system under stress, the first step in coping with it is to reduce the stress on the system - this is what low carb is about. You take carbs out of the diet, reduce the amount of glucose arriving in the body, and hopefully give your insulin system a bit of a break. Many of us find that our systems can work well enough with somewhat lower levels of carb, so that there isn't unmanaged glucose floating around , and consequently insulin levels should also fall. As with any system that's been under strain, putting the same load on it again is likely to result in exactly the same problems - so low carb is a way of managing, not "curing" the problem symptom.
Is that helpful? Unfortunately there is so much misinformation around that reading stuff on the internet can be less than useful. The media are probably responsible for most of it. If you're not sure about anything, please ask.