Yes, but we still correctly understand the scene to be conveying the message "this character is dead," regardless of whether we believe it. It's a language. Certain symbols and behaviors are collectively understood to carry certain meanings. A man lifting up a body-shaped sheet, looking under it, and looking away, is as clear and straightforward as spelling out the words "this man is looking at a dead person's face." We all know exactly what it means. If you later in the story *reveal* that you faked out the audience, and he was an archaeologist looking at a damaged mummy, or something, that's perfectly legit, sure, but it doesn't change the fact that - in fact, it relies entirely on the fact that - you were supposed to see the initial image and get "oh, guy looking at dead body" out of it.
Likewise, we were supposed to look at the slide under the table as sex. Saying that the fanbase reading it that way is some kind of failure on the fans' part is disingenuous at best.