No, it’s not. It’s on Standard too.

If an attempt is made to enable it on any other edition, you’ll see error 865 written to ERRORLOG “Buffer pool extension is only supported on Standard and Enterprise Editions of SQL Server.” and the same exception is raised aborting the ALTER SERVER CONFIGURATION statement.

It’s also worth knowing that Buffer Pool Extension is only supported if running on x64 architectures and not running under the Wow64 environment.