This was the pre version 2.3 method of mirroring and object. You need to be careful when following tutorials found on the web. A lot of them have not been updated.
Pretty weird since this one’s off blender3d.org.But the tutorial is a little vague anyway.I’ll try experimenting myself from now on.80% of the people who make tutorials arent good at it.
You got that right. Its not that they are not good at using blender. Its just that they are not good at explaining what they are doing. They know the program or a certain technique like the back of their hand. But they forget that they are trying to explain it so somone that does not know it. So they skip steps that they would automatically do. But the reader may need to have those steps explained.