It is really shocking to me that this isn't more of a thing. If the I/O block size is 4,096 bytes and you are doing things like updating a user's email address

It is really shocking to me that this isn't more of a thing. If the I/O block size is 4,096 bytes and you are doing things like updating a user's email address or some boolean preference, you could get a LOT more data packed in per unit space & time. Each block is enough to store an entire page of text or a small image. The only caveat is that the system needs to be consistently under heavy load, or you would have to force clients to wait unreasonable amounts of time for a sufficient batch to accumulate. I think the best goldilocks path is to put something like a MPSC ring buffer in front of the command processor and to "take what you can get" in terms of batch size each iteration.