ARM template for Shared disk create and attach is removing the existing data disk when attached - arm-template

Question

When trying to add the shared disks to a existing VM with data disks, the existing disks are removed from the Virtual machine as part of ARM template deployment. Below is the ARM template.
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"Shareddiskname": {
"type": "array",
"metadata": {
"description": "description"
}
},
"location": {
"type": "string",
"metadata": {
"description": "description"
}
},
"vmname": {
"type": "array",
"metadata": {
"description": "description"
}
}
},
"functions": [],
"variables": {},
"resources": [
{
"type": "Microsoft.Compute/disks",
"apiVersion": "2021-08-01",
"name": "[parameters('Shareddiskname')[copyIndex()].name]",
"location": "[parameters('location')]",
"sku": {
"name": "StandardSSD_LRS"
},
"copy": {
"name": "shrdcopy",
"count": "[length(parameters('Shareddiskname'))]"
},
"properties": {
"creationData": {
"createOption": "Empty"
},
"diskSizeGB": "[parameters('Shareddiskname')[copyIndex()].diskSizeGB]",
"maxShares": "[parameters('Shareddiskname')[copyIndex()].maxShares]"
}
},
{
"name": "[parameters('vmname')[copyIndex()]]",
"type": "Microsoft.Compute/virtualMachines",
"apiVersion": "2021-03-01",
"location": "[resourceGroup().location]",
"copy": {
"name": "vmcopy",
"count": "[length(parameters('vmname'))]"
},
"dependsOn": [
"[resourceId('Microsoft.Compute/disks', parameters('Shareddiskname')[copyIndex()].name)]"
],
"properties": {
"storageProfile": {
"copy": [
{
"name": "dataDisks",
"count": "[length(parameters('Shareddiskname'))]",
"input": {
"name": "[parameters('Shareddiskname')[copyIndex('dataDisks')].name]",
"lun": "[parameters('Shareddiskname')[copyIndex('dataDisks')].lun]",
"createOption": "attach",
"managedDisk": {
"id": "[resourceId('Microsoft.Compute/disks',parameters('Shareddiskname')[copyIndex('dataDisks')].name)]"
}
}
}
]
}
}
}
],
"outputs": {}
}
validation of template with -whatif shows the below output-- its replacing the existing disk 01 and 02 with shared disks. How can I add the shared disks with existing data disks
~ Microsoft.Compute/virtualMachines/testvm01 [2021-03-01]
~ properties.storageProfile.dataDisks: [
~ 0:
- caching: "None"
- toBeDetached: false
- writeAcceleratorEnabled: false
~ lun: 0 => 2
~ name: "01" => "sharedsk-01"
~ 1:
- caching: "None"
- toBeDetached: false
- writeAcceleratorEnabled: false
~ lun: 1 => 3
~ name: "02" => "sharedsk-02"
]