The HTML and CSS courses should tell when an html element is a void element before people try to use them, having them guess if they are or not is not really constructive to the learning experience when the only way to know if they are void or not is to know in advance.
Do you have an example of a step where an element is introduced and an example doesn’t clarify that only a single tag is needed?
When a new void element is introduced, the instructions say that it is a void element