Provision sub site using PnP Site provisioning schema?

I did all try using the sub site structure migration using your mentioned commands for our project. Its only migrate the Site collection level structure not sub site level structure. 

What I observe is subsite level structure migration shows things to be done in PowerShell log trace but actually nothing get created in the targeted subsite.

Then i need to call Apply-SPOProvisioninTemplate multiple times and split this up in multiple xml files.

Example

Apply-SPOProvisioninTemplate -web subweburl1 -Path c:\temp\template1.xml

Apply-SPOProvisioninTemplate -web subweburl2 -Path c:\temp\template2.xml

Apply-SPOProvisioninTemplate -web subweburl3 -Path c:\temp\template3.xml

Apply-SPOProvisioninTemplate -web subweburl4 -Path c:\temp\template4.xml

What i would like to do is

Apply-SPOProvisioninTemplate -web rootsite -Path c:\temp\rootsite.xml

And rootsite.xml contains something like

<SubSites>

<SubSite url="subweburl1">

  //Stuff here :)

</SubSite>

<SubSite url="subweburl2">

  //Stuff here :)

</SubSite>

<SubSite url="subweburl3">

  //Stuff here :)

</SubSite>

<SubSite url="subweburl4">

  //Stuff here :)

</SubSite>

</SubSites>