Flash block size generally affects only writing (and things related to that happen on the on-device FTL, not in the kernel, except for embedded raw flash device

Flash block size generally affects only writing (and things related to that happen on the on-device FTL, not in the kernel, except for embedded raw flash devices that require specialized filesystems). There is a general readahead in Linux though, see eg blkdev(8). For many use cases the small randomish iops rate is the bottleneck (think database index), and because of the small latencies in flash storage you often want to keep the readahead modest absent some detected pattern of sequential io.