Like James said, if you turn up any flasher enough, you’ll have clutter on the screen. Happens on my LX-3, my buddies FL-20, and any other flasher I’ve seen or used.
I did not have clutter on my Ice-35 unit with the gain set properly for fishing, though. This was using various smaller presentations (slender spoons, diamond jigs, gill pills, etc), in 15-25 FOW. No problem marking the small lures, and no clutter on the screen. Unless my ‘bird is an anomaly, I’d say there is something wrong with your buddy’s flasher. If I were him, I’d be making a call to Humminbird customer service.