I'm not saying it's not useful. I'm not dismissing it.How is it a false equivalence if the majority of your bandwidth consumption can be controlled in a manner that can consume the bandwidth of the 32MB effectively and limiting the consumption required by the external RAM? This is the very nature by which a TBDR operates, but even well controlled immediate mode renderers can make effective use of it, especially in a closed platform.
If [complex hypothetical]... if you need a hypothetical to make it equivalent, it means it's not. If the bandwidth required for that 32MB is about 3 times more than the rest of the memory, sure you would get that bandwidth. Is that a reasonable ratio? In what kind of code is it attainable? I don't know, and it depends. That's why it's a false equivalence.