What they're referring to is a fairly common phenomenon called semantic satiation, though in this case for visually seeing the word rather than audibly hearing the word.

Funny. How many times have you overlooked the the trick when someone puts too much of a commonly seen word in a sentence?

Or did you miss that I put 2 "the" words in the sentence above?

I'll give you the benefit of the doubt. Perhaps you're taking what I said literally. Using fake in the sense of "does not exist", as opposed to "no longer appearing real". So, when the human mind looks at our world it perceives patterns in every environment we're in. Eyes. Seeing and perceiving. For most of us this is the most prevalent and important sense.

The processing of information is, however, not perfect. Because we are so good at identifying patterns, we quite literally trick ourselves. Sometimes it's because we can ignore a part of our environment safely, other times it's because there is something we identify and can't comprehend visually without more context. In the case of a repeating word, this is reactive inhibition, or to put into context: The brain recognizes that the same process is repeating over and over. It seeks to combat this stimuli by making the reactions from the neurons less responsive. It suppresses the usual reaction.

Thus a word, while real because it's a word, begins to feel as if it's somehow lost its meaning.