Harold Bloom claimed that he could read 500-700 pages in an hour (which, even without delving into it, is simply ludicrous).
Dan Schneider from the e-cosmoetica website claimed that he read David Foster Wallace's Infinite Jest within 7-8 hours, justifying himself by saying that it was so bad that he "cut through it like water".
The only major problem with that statement is that Infinite Jest has a word count of over 500,000, meaning even if he read the entire novel in 8 hours, he would have had to read over a thousand words every minute on average. According to cognitive neuroscientist Stanislas Dehaene, speed reading of up to 1,000 words per minute "must be viewed with scepticism", so for Dan Schneider to surpass that pace for more than 8 hours straight is beyond ludicrous. For professional speed readers who claim a 1000-2000 wpm pace, they, on average, can only retain approximately 50% of the information read.
I feel like it's a very odd thing to lie about, and it seems to stem from some need to justify their intelligence to the public.
I think it's an important asterisk to put next to these literary critics when it's possible that they haven't even actually read some of the literary works they are critiquing and have simply skimmed them.