"Wooden Shield" and "Enhanced Wood Shield" can't be used at the same time

[rodrigomorales1]

I'm trying to use the same armor set that is shown in the main page of this repository (see green arrow in screenshot below). Note that, in the screenshot, there are two shields being used. However, when I try to use two shields in the game, I can only use only one of them (see videos below), in other words I can't use two shields as shown in the main page of this repository.

I was thinking that one possibility is that the screenshot is trying to demonstrate that there are two types of wooden shield, but it is not trying to demonstrate that the player can use two shields at the same time. If that's the case, then it implies that at any time at most there will be five armor slots being used, so my question is: what's the use of the sixth armor slot in the game?

In the video below, I use the "Wooden Shield", then the "Enhanced Wood Shield", but only "Wooden Shield" is placed in the slot.

1.webm

In the video below, I use the "Enhanced Wood Shield", then the "Wooden Shield", but only "Enhanced Wood Shield" is placed in the slot.

2.webm