All previous installs to version 9 had a folder structure like this:

/Data
/Databases
/Website

Now in version 9.x the /Data directory is nested inside the /Website root. SIF default logic even has code that places it there.

"Site.DataFolder": "[joinpath(variable('Site.PhysicalPath'), 'App_Data')]"

Just curious if this was intentional?
No performance worries about indexes due to Solr files in a separate directory?
To support Azure deployments?