When drive formatting the Operating System will create what is called a Block size. The block size is the OS's logical grouping of space to deal with data placement of files etc…
Live Optics makes great strides to always use the term IO transfer size since IO Transfer Size does not equal formatting Block size.
"Block level storage" by nature is sending data in data fragments, but not inheriting it's name or value from the OS value with similar naming. These are often confused and therefore we refer to size of the IO data transfer as "IO Transfer Size."
So you can have a 512K formatted disk drive and you can send 4K IO transfers all day long.
Likewise, you can have a 4K formatted disk with applications sending out 32K IOs all day long. And of course they could be equal as well.
In fact, many applications will optimize this on the fly. Modern SQL for example can change IO packaging between tasks like maintenance routines vs. regular DB activity.
So the next time you hear someone say "What is the block size?" be sure to clarify what they mean!