Re: Is this new?
Chinook had 2 sets of heads on each platter
This sticks with one head per platter, and is essentially stacking 2 HDDs in one case
heads in an assembly are accessed individually, not in parallel, because thermal (and other) effects mean that calibration will almost always be out if parallel access is attempted. The only way to allow 2 heads in the stack to be active is to have them pivoting independently (ie: two voice coil actuators, etc) and the complexity is hideous whether you do it with two independent head assemblies on each side of the platters (Chinook) or have two mechanically separated head assemblies on the same pivot
Whilst Seagate et al ate putting a brave face on it, SSDs have been taking their lunchboxes away for quite a while. They shut down their main research labs a decade back and HAMR/.MAMR is taking a long time to bring the holy grail of reliably increased density, whilst the shenanigans in the wake of the 2011 Thai floods convinced a lot of buyers that getting away from mechanical drives (supply choke points and opportunistic profiteering vendors) was a worthwhile pursuit - last year's shenanigans with submarined prosumer drives being slipped into NAS channels didn't help their cause..
As much as they talk up these capacities, Soiid state is closing beat them on longevity/endurance a long time ago and is closing rapidly in on mechanical device cost at all densities and a lot of buyers are minded not to reward past bad behaviour by actively avoiding by giving HDD vendors their SSD purchases