Hi there,
I think there's a few aspects missing from this question - specifically I think you are probably talking about LUN block size, which doesn't (directly) relate to actual disk blocks. Someone you are talking to may have misunderstood some of nimble's marketing - they used to love saying how NetApp "only" did 4K blocks, while nimble could do "variable length blocks" (which are then written to disk in 4K chunks.. like NetApp systems, but I digress..)
The short answer is no - the block size is not changable on the NetApp side.
But the longer answer is to try to understand how the storage is being used and what problems are being seen.
Are you running Storage Replica on the Windows server, with an aim to multisite replication? What problems are you seeing? Slow initial sync? What sort of performace are you getting? What level do you expect? What is your WAN/LAN connectivity like?