He meant CRT's not LCD's.
Flat screen in CRT means that the tube will have to bend the rays much harder than in a round screen. That means that the flatter the screen is, the more prone it will be to outside disturbance (magnetic fields) and calibration errors during manufacturing.
Having said that, a quality screen is a quality screen. It doesn't really matter how flat it is as that's not a factor. Read some reviews, pick your choice and remember to visually check the exact screen you will buy.
6-7 monitors coming out of the production line will have smaller or bigger calibration errors - that means that if you compare two identical CRT's with eachothers, the other can be bright, crisp and vibrant where the other brand new identical crt can be blurred and lack contrast.
Always, always check your CRT before buying - or at least prepare to return it the day after you get it.