It would appear that there is a small error in the documentation regarding architectApi. As an example:
see https://developer.mypurecloud.com/api/rest/v2/architect/index.html
select any of the API calls, then select usage and Javascript.
var api = new platformClient.architectApi();
should be:
var api = new platformClient.ArchitectApi();
I am using the platform-client-sdk-javascript-beta.
FYI