What you are trying to explain is a concept belonging to a deduplication appliance, while on ReFS things work differently.
First, those are the block size used to store files in the file system, but then Veeam writes its own blocks at different sizes, depending on the deduplication level; "local" is the default and is 1MB before compression. Suppose this block is compressed to 512KB, on a 64k refs volume it will consume 8 blocks, while on a 4k volume it will consume 128 blocks. But what is going to be cloned is the Veeam block, not the single volume block, so in both cases the final effect in terms of cloning will be the same. But in no situation refs blocks are compared to others, as there's no deduplication in refs volumes.
EMEA Cloud Architect @ Veeam Software
Veeam VMCE #1