After spending a bit of time with the debugging console, I see what @agmontpetit is saying and agree. If you enable debug mode for the GA tag, you can see that it creates a new tracker each time a virtualPageView occurs, which as the Google link points out is undesirable.
That said, I am still a beginner as I mentioned, so I’m going with the All Page Views load method for now, but will be trying to do some external validation somehow
Based on this reading, it appears that the Discourse GTM part is implemented correctly:
With Google Tag Manager, every single Universal Analytics Tag that fires on the site creates a new, unique tracker object.
The above linked post described the issue Google is trying to warn you of:
This means that the Document Location field is updated with every Tag you fire, which is a problem if the URL changes due to browser history manipulation. Thus you can end up with a situation where the first Universal Analytics Tag has
gclid in the URL, attributing the session to AdWords, but the next pageview doesn’t have this in the URL anymore, as you would not include it in the “virtual” pageview path names. Instead, since
gclid is no longer in the URL, GA looks at the HTTP referrer of the page to see what the previous page was for attribution. It finds
google.com , as you came from the search engine (HTTP referrer is not updated when manipulating the URL with the browser History API). Thus a new session starts with attribution to Google Organic! I’ve dubbed this as the Rogue Referral problem.
The post provides several solutions on how to deal with the problem, hopefully they work