The word Theravadin means "Way of the Elders". Theravadin Buddhists call themselves "Theravadin - the Way of the Elders". Tibetan Buddhism is part of the Mahayana school of Buddhism. Theravada and Mahayana are two different schools, very distinct, very different. The Mahayana school of Buddhism includes Tibet, China, Japan and Korea. Theravadin went into the Southern area: to Burma, Sri Lanka, Cambodia, Laos and Thailand. So the terms Theravadin and Mahayana are the terms that Theravadin Buddhism uses.
Mahayana traditions unfortunately use the terms Mahayana and Hinayana. Mahayana is translated as the "Great Vehicle," Hinayana as the "Lesser Vehicle". So when the Tibetans or other Mahayana people refer to Theravadin as Hinayana, it is actually very derogatory, and simply not nice. By saying this is a "small car," a "Small Vehicle," it's a superiority complex, ego trip we feel that the Mahayana school has developed. Generally, Theravadin doesn't worry about it, just gets on with its practice. But for some reason the Mahayana school wants to keep criticizing the Theravadin.
The Theravadin school is usually much more content. We are not going to waste time cutting them down all the time. We are going to get on with the real practice. So with regard to this term Small Vehicle/Hinayana that they use, it is best to throw that out of your vocabulary, not to accept it.
One person made a little play on these words. They said it's like there's a parking space in front of a building, which is not for parking at, only for dropping off someone. There's a sign at that space and it says, "Big car or small car, they all get towed away at owner's expense". Can you can understand that in regard to your spiritual practice. Hopefully we are all going on the same trip. It's best not to get caught up in thinking we are better than others, or worse than others and all that, "I have the bigger car, I have the slower car." You know, take a nice Mazerati, right, sit back and zoom around the place, right? It goes from Berlin to Munich fine, right? So does an old beetle Volkswagen, goes from Munich to Berlin. Some people tend to think they can go faster. Yeah, true, yet the faster they go, the more chance of accidents they have, right?
The question mentioned that the Tibetan Buddhists consider physical exercises as most important. I don't know this as a fact, but I do know that they are into some physical exercises or physical postures as part of their purification. They have something called, I think, 10,000 prostrations. They do a very big kind of bowing towards the Buddha statue and they have to do it 10,000 times as part of their training. Ok, maybe they think that type of exercise is important. And I would agree that doing exercise in general is important for keeping healthy, but I would not agree that it's a way to purify our minds and hearts.
I will mention that because the Mahayana school went north, they did have historical problems with staying in shape physically. This is real. The Kung Fu martial art training comes from a Buddhist Monk. The Buddhist Monk discovered that when he was teaching his students they would fall asleep a lot. It was a cold climate, and they didn't have the heaters we have today. The teacher started teaching a type of physical exercise to give his students more energy, which evolved into Kung Fu martial arts.
Also going on alms round was something which declined in the Mahayana school, to the extent that many of their Monks today work as farmers and normal jobs to make money, etc. Thus their Monks did not get that exercise every day. When Buddhism went south into the warmer countries, the Monks still went on the morning walks to get their food. The Monks at our Wat walk 3, 4 or more kilometers every morning up and down the hill, and around the villages. They get exercise every single day, just by having that super long walk.
Last part of the question, "Do you know how it came to such a different view according to the scriptures?" According to the scriptures there is nothing there for that, but maybe the background I just mentioned.