I believe so, just wanted to confirm a couple of things>

1. So long as we are using an application to directly invoke the business service, this means the business service doesn't strictly need an OnProcessInput() method?

2. Is the General method thus being called how you described above, i.e. OnTask() --> General() ?
3. Just to confirm I'm grasping the concept, would this be an example of the business service being in the data "pushing" mode as detailed in this link: https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KE… ? 
Thanks very much for your help and input, it is very appreciated by a new dev like myself!

Apologies I have not been able to answer until now.

The business service has no adapter as verified by looking at its code as well as its settings in the configuration.

However, it IS tied to a REST Service of which I was previously unaware. An HTTP request is sent with either POST with a payload or GET with the data listed in the URL. When the associated class method fires, it instantiates a request with information from the HTTP request and a response class and uses them as arguments in the General() method.
This solves what Sean raised about the method firing off more than once. My question now would be is it permissible to have a business service with no OnProcessInput() method so long as it is tied to something like a RESTful API? I am a newer developer when it comes to Ensemble/ObjectScript so I am under the impression that OnProcessInput() is the end-all-be-all when it comes to the business service.

Please let me know and thanks for your responses thus far.

Hello and thanks for this well thought-out response!
In terms of adding to the headers, do you know what method I would use to add them? The Microsoft identity platform requires three different parameters for what I am trying to do and the research I've done into the %OAuth2.JWT.ObjectToJWT method I can't seem to figure out how to add them, or maybe it doesn't have that capacity?