I'm a believer. Partly because of my own experience and partly because I just like the thought of a few monster cutts swimming around out there!
I've put eyes on two src that would have challenged for the state record. Not a doubt in my mind. One followed a fly right up to my rod tip before turning away when I was beach fishing years ago. But the biggest one I saw 3 separate times in the same area. All 3 times it followed a fly to the boat, just appearing like a ghost as the fly got close, and then casually turned away like it never had any actual interest in eating. First time my buddy in the bow saw it and I didn't. He was almost white and shaking at the knees. He just kept saying "oh my God it's so huge". He's an incredibly experienced fisherman and I didn't doubt him in the least. Few days later on a different trip in the same area, I saw it with my own eyes. Absolutely monstrous, and most definitely a cutthroat. I saw it two other times in the same area that same year, but haven't seen it since. Probably 4 years ago.
Haven't seen anything close to that size since, but I definitely believe.