Either 2 or 3 body paragraphs is enough to develop ideas and show your ability to organise paragraphs. With 2 or 3 body paragraphs, you can get a high score. When you read your essay question, you plan your ideas and then decide how many body paragraphs to have (2 or 3). You should not decide this before you enter the test. The number of body paragraphs will be decided by the type of question and your ideas. See my model essays on this page:
If a paragraph is too short, it may be because the initial idea has not been developed sufficiently. To some extent, the level of development is dependent on the writer's purpose and the overall length of the essay. However, you should beware of paragraphs of only two or three sentences. Read them carefully and consider if your idea has been sufficiently developed.
How many paragraphs for an IELTS essay?
Although I have seen your sample essays that all contain 2-3 body paragraphs, but still its confusing because you also mentioned that to increase the score 4-5 body paragraphs are required.
3.1 Writing the Short Essay - The History Guide -- Main
Three hundred word essays can be some of the most difficult papers to write because of the tight length constraint. These essays are often about a very specific topic and require a lot of thought. This essay is just over 600 words, so for reference, your essay would be half of this. Not very much space at all! Here is a basic tutorial on how to write a 300 word essay.