I don’t know if this will help but IBM 3380 DASD used multiple platers and arms. Each arm had 2 heads one for the top and one for the bottom of each platter. The heads “flew” above the surface. The air system had to come up before the platters were allowed to spin.
Admittedly they were not 3.5 “ platters and they were not trying to”seek” a TB of date in nanoseconds. I would suspect inertia, mass, etc. would be a challenge in the speeds and capacity of todays small drives.
That’s quite logical to this layman.
Thx.