First time I hear of the CRT collective, very interesting. Thanks for sharing, I'll definitely look into that community.
Yes probably the non Japanese brands might be more likely to have 50hz compatible models. I'm pretty sure most Japanese brands didn't release 50hz compatible tv's in the States, Sony, Hitachi, Panasonic, probably Toshiba but I'm less familiar with their line ups. I wish they did.
As for the sensitivity of earlier tv's I think it's also the move to digital chassis, and also the silver case tv's of the 2000's generally have less good shielding in my experience. You can see it even just opening up the back. The result is sometimes one can catch interference on the signals of these tv's, not even talking about interference from the surroundings, but even just internal interference. I've seen it even with the better models, if you display solid colors depending on the source you might see some kind of very faint lines of interference when up close. Still to me it's a worthy trade off because many of these tv's produce the best colors, sharpness and general picture that I've found on consumer tubes.
Anyway my impression is that these same sensitivities are possibly what causes these minor picture fluctuations when running off ntsc standard video. Again I have to stress that to many viewers it may not be a problem, maybe many would not even notice them, but it's generally there nevertheless and to those who do catch these picture anomalies it can be very irritating.
By the way Recap, I didn't know the story of SNK showing off their goods on PVM's, good stuff. I think there's a lot to like in PVM's, these monitors were very much ahead of their times in many ways, but to me it's just that the picture on these rarely looks like what I expect from a crt, meaning what I was used to seeing both in arcades and in homes throughout my childhood.