If you type n now, you get an error message saying that this node has no next node. Similarly, if you type p, the error message tells you that there is no previous node. (The exact message depends on the Info reader you use.) This is because n and p carry you to the next and previous node at the same level. The present node is contained in a menu (see next) of the node you came from, and hence is considered to be at a lower level. It is the only node in the previous node’s menu (even though it was listed three times). Hence it has no next or previous node that n or p could move to.
If you systematically move through a manual by typing n, you run the risk of skipping many nodes. You do not run this risk if you systematically use SPC, because, when you scroll to the bottom of a node and type another SPC, then this carries you to the following node in the manual regardless of level. If you immediately want to go to that node, without having to scroll to the bottom of the screen first, you can type ].
Similarly, BACKSPACE carries you to the preceding node regardless of level, after you scrolled to the beginning of the present node. If you want to go to the preceding node immediately, you can type [.
For instance, typing this sequence will come back here in three steps: [ n [. To do the same backward, type ] p ].
Now type ] to go to the next node and learn about menus.