This math assumes that the requests are serial (each begins and completes before the next one starts), rather than concurrent.
An org might deploy a complete copy of the monolith for a single tenant, and it would still be a monolithic architecture.
Native Command Queuing (NCQ) [1] is a SATA extension that lets the drive optimize the order commands are performed in. For HDDs, this means it can do the commands in an order that minimizes overall seeking time. For SSDs, it can concurrently execute commands that are operating on different physical chips.
I can't find a good reference, but it seems like this is also true for RAID volumes, which are almost certainly being used on the server -- the RAID controller can perform parallel reads on each of the independent disks. How well this works is highly dependent on the RAID controller itself.