I don't know about "feels", unless he has some serious synesthesia issues, but it's far from unheard of to be able to see it.
Speaking from personal experience, I have two data points to contribute. I have been able to see a flicker quite clearly from my peripheral vision coming from an LED christmas light fixture. I remember this clearly as it was so distracting that I had to reposition my body during the conversation to face away from it entirely. In another instance, it was noticeably irritating the first few minutes I ever sat in front of a television in Europe (being used to the higher refresh rate in the US).
Speaking from personal experience, I have two data points to contribute. I have been able to see a flicker quite clearly from my peripheral vision coming from an LED christmas light fixture. I remember this clearly as it was so distracting that I had to reposition my body during the conversation to face away from it entirely. In another instance, it was noticeably irritating the first few minutes I ever sat in front of a television in Europe (being used to the higher refresh rate in the US).