Really? I have a hard time believing that. The concept has been around since the 80's, if not before then. Should we be putting scare quotes around the word "Mouse" when we use it to refer to a computer mouse because it's not a literal animal mouse?

There are probably way more people familiar with computer mice than video games.

that's like saying people who don't use computers won't understand that text is in a computer even though it has the same meaning as, say, text in a book

Item in plain English means basically anything that can be counted, usually something small. Item in a video game usually means something players can pick up, maybe use, and drop, as opposed to something that's part of the environment. Item in Minecraft has a technical meaning, basically anything that can go into a hopper inventory, as opposed to particles, blocks, mobs, stuck arrows, other entities...

saying there is an item called a book in minecraft will not go over the average person's head