SqlServiceAccount: Parameter RestartService can only restart Database Engine service

Details of the scenario you tried and the problem that is occurring:
The resource xSQLServerServiceAccount when used with parameter RestartService can only restart the Database Engine service. It is not possible to restart any other service it support changing the account for.
Also, it will always restart Database Engine when using parameter RestartService regardless if it was the Database Engine that was changed.

The DSC configuration that is using the resource (as detailed as possible):

xSQLServerServiceAccount SetServiceAcccount_User
{
    SQLServer = 'TestServer'
    SQLInstanceName = 'MSSQLSERVER'
    ServiceType = 'ReportingServices'
    ServiceAccount = $ServiceAccountCredential
    RestartService = $true
}

Version of the Operating System, SQL Server and PowerShell the DSC Target Node is running:
Windows Server 2016, SQL Server 2016, WMF 5.1

What module (SqlServer or SQLPS) and which version of the module the DSC Target Node is running:
SQLPS

Version of the DSC module you're using, or 'dev' if you're using current dev branch:
Dev

Start by locating the xSQLServerServiceAccount resource and its tests, then trace how ServiceType and RestartService are handled for ReportingServices. Done means changing a ReportingServices account restarts that service, while changing another service does not always restart the Database Engine.