ReFS vs NTFS - which is better for SQL Server 2019 on Windows Server 2019
So I'm not familiar with Nimble Storage or ReFS but it looks like the manufacturer (HPE) recommends against using ReFS with Nimble Storage, as a quick Google search turns up on their documentation here.
That being said, what is your Server Admin trying to achieve with Nimble Storage and/or ReFS?...this is definitely a very edge case setup as far as SQL Server goes (the majority of instances in the wild are likely running on NTFS).
In terms of reliability (which it seems like the point of ReFS is), from a database perspective, having a data redundancy, backup, and recovery plan that keeps RTO (Recovery Time Objectives) and RPO (Recovery Point Objectives) in mind is what would be recommended. Whether those objectives are accomplished through appropriately scheduled Full, Differential, and Transaction Log backups, implementing Availability Groups, or any other related means, none of them will be dependent on nor recommend a specific file system for your server's disk.