In your examples, it's not the brackets signifying the multiplication. It's the adjacency that signifies the multiplication (as in e.g. 3x) and in they happen to need brackets to highlight the precendence which would be lost in e.g. 3x + 5.
The notation of the article logically follows because e.g. (4) = 4 but using that as a "cheat" to enable multiplication of numeric literals using adjacency is very rare I think.