Items in 3rd person don't use back-face culling, which causes a few issues.

For one, items/blocks don't render like this anywhere else in the game. Now I don't like back-face culling, but having it gone here and nowhere else isn't that great.

Secondly, it causes Z-fighting in certain scenarios:

Cross-models. even though they consist of only 2 elements that don't overlap, opposing faces (east and west, north and south) render even though they shouldn't. Attached is a debug pack that includes an arrow model that is affected by this.

Anti-back-face culling tricks. While the option "two-sided" existed for a short time, that was removed and now there is no supported way to disable back-face culling on faces or elements/blocks. Devs will respond to that with "just use an inverted element" which, due to this bug, results in z-fighting unless compensated for (especially when it may otherwise not be needed).

General models. Because some people might make models based on the fact that back-face culling exists everywhere else in the game, it's odd to have it in one place where it's permanently off for everything.