Hi,
I did a research ,GPOs for the Task Schedule on the servers 2016 and 2019 show the same thing, the windows server 2016 was not in the list.(Means it is the same with the settings on 2008R2 DCs.)
So it is the expected thing by default. It would be ok to select the windows 8 or R2 :If you want to deploy policy for servers and clients with newer version.
Here is the screenshot in my 2019 DC:
But if you open the task schedule on the DC, right click the task and select the properties, you can see the server version for the server ,such as 2016,2019 as following:
Best Regards,