“Flat” and “flat screen” arent the same thing. CRT TVs had a curved glass screen. Due to the fact that the rear projection could just project across the curve. With technology advancements they were able to improve picture clarity while flattening the screen. These were still bulky projection style TVs, but were called flat screen. But then when actual “flat” TVs (in the form of LCD, etc) came around people kept using the term. So a flat screen TV could be very thick.