Explanation
Applying locks can lead to unexpected results because some operations that don't seem to modify the resource actually require actions that are blocked by the lock. Locks are inherited to all of its resources if it applies on resource group level.
Upload a blob to storageaccount1 is possible if we have readonly lock on RG1 since we are trying to modify the data not resource properties.
When a R/O lock is put on a resource, you lock it's properties not the resource. So while a read only lock is present on a storage account(inherited from a resource group), a file can still be uploaded to the already existing container of a storage account.