Thank you for pointing this out!
PI API 2018 is indeed supported in Windows Server 2016 and Windows 10. This is shown in the release notes but not in the System Requirements page.
Please make sure that the PI API 2.x only supports Windows Authentication(i.e. PI Mapping). If you have been using PI Trusts, then your interface/API application will not be able to connect.
I will send a note to our team about the webpage. Thank you!