Thank you for asking this question on the Microsoft Q&A Platform.
In general, when you mount an NFS the data must travel by the network, your blob storage is an "NFS" located in another data center (if your environment is on-premises), so latency is expected.
Also, it will depend on the configuration of your storage account, your environment, and the network.
Hope this helps!
Accept Answer and Upvote, if any of the above helped, this thread can help others in the community looking for remediation for similar issues.
NOTE: To answer you as quickly as possible, please mention me in your reply.