That's only partially true - the GDDRX you'd find on say a 3090 is physically very different than what you'd find on a strix halo or mac or vanilla ram. e.g. runs 4 voltage levels not 2 so that it can transmit twice the info per cycle
Well, what they don't tell you about GDDR6X is that it's 4 voltage levels but it never goes from min to max or vice versa in a single transition (PAM4 MTA). It transfers 1.75 bits per cycle.
And then GDDR7 backed off to PAM3 and sends 1.5 bits per cycle.
There's a good chance [LP]DDR will use the same techniques once it gets into the same speed range.
