My personal opinion is that it all depends on how deep or shallow (how subjective or objective) the POV is.
A narration from a "shallow" or very objective POV may be limited to stating facts. Like, "As Mary entered the house, John noticed her keys tinkling and grimaced. She stared him, as if she could read his mind, and asked, "What's wrong with you?" This is purely objective but still from John's POV. The tinkling is mentioned only because JOHN, the POV character, noticed it, otherwise it wouldn't have been observed. It's also indicated that he grimaced, meaning he somehow disliked it, but without explaining exactly why. When she stares at him, she does it "as if" because the POV character can't actually know what she's doing or taking place in Mary's brain. He can only speculate. In this case, rewriting the line as "She stared at him, reading his mind ..." would be a clear POV shift.
A narration from a "deep" or very subjective point of view comes from the depths of the POV character's mind and much resembles a first-person POV narration, even though in third person. "As she entered the house, the ominous tinkling of the keys set off every alarm in John's mind. The same tinkling he had heard as a kid before his mother's murder. Mary was the right age. Had she done it? Her movements that night had never been fully explained. John grimaced, he couldn't help it. She stared at him, reading his mind. She knew he knew. "What's wrong with you?" she asked in that velvety, menacing tone.
The above narration comes completely from the character's POV. The tinkling is only ominous because he perceives it a so—in the first, objective narration, it's only a sound. The important part is when she stares at him and "reads" his mind. No reader—maybe only a few POV-Nazis—will perceive it a POV shift but clearly as John's guess. Whether or not accurate is another kettle of fish, but it's his guess, not POV shift. If this little paragraph were a full story, the extra context would provide the answer. If he has been digging into his mother's murder, and Mary, the actual murderer, learns about John's digging, this could have been a moment of truth for both of them because both could have remembered that her keys tinkled when she entered John's house gun in hand. John's grimace, his expression, could have allowed Mary to guess that he has finally put together the whole puzzle and has discovered her. On the other end, her own expression, the staring, accurately allows John to guess that she knows that he knows. This happens in real life all time given the proper context and background without the need to read other people's minds or get into their bodies for a short while.
So, conclusion: whether it's an POV shift or not, whether you need to use "as if", depends on how deep, how subjective, your narration from a particular POV is. Should it be subjective, or "deep", enough, then you can avoid the "as if"s because it won't be a POV shift, but part of the subjective narration. If your narration is more objective, describing the reality through the POV character's eyes, but not involving the POV character's opinion, thoughts, and feelings, then you need to use "as if" to make it clear you're not shifting the POV, but still judging the event with objective eyes.
My humble opinion.
Kiss,
Gacela