You're correct, this particular problem can be handled with sufficiently sophisticated frame buffer logic. I was generalizing from that to other concepts where emulating the television or its signal processing would be required.
I'll give you another example. On the Atari 2600 game console, the vertical sync is software controlled. The software is responsible for enabling the vertical sync pulse. This can be done 60 times per second as standard -- or you could play tricks with it. Suppose you strobe it at a different or even irregular rate. On an analog TV, the picture starts rolling vertically. That breaks way outside the sandbox of a framebuffer, with signal being displayed in overscan areas, and during the normally-blank retrace interval resulting in ghosting effects. (No commercial game did that, but it's been done in tech demos, and conceivably a horror game could do it intentionally for mood.) To produce that same behavior on framebuffer-based hardware, you need to emulate or at least approximate the workings of a TV's vertical sync logic, none of which appears in the console itself.
I'll give you another example. On the Atari 2600 game console, the vertical sync is software controlled. The software is responsible for enabling the vertical sync pulse. This can be done 60 times per second as standard -- or you could play tricks with it. Suppose you strobe it at a different or even irregular rate. On an analog TV, the picture starts rolling vertically. That breaks way outside the sandbox of a framebuffer, with signal being displayed in overscan areas, and during the normally-blank retrace interval resulting in ghosting effects. (No commercial game did that, but it's been done in tech demos, and conceivably a horror game could do it intentionally for mood.) To produce that same behavior on framebuffer-based hardware, you need to emulate or at least approximate the workings of a TV's vertical sync logic, none of which appears in the console itself.
(I know this from experience, I wrote an Atari 2600 game: http://www.dos486.com/atari/ )