I thought the article was interesting and worthwhile, but also was disappointed there wasn't more discussion about the context you're pointing out. I don't know anything about it outside of what's stated in the article, but it seems based on what was written there was enough uncertainty about the context surrounding the document to raise questions about the authenticity of the story or the document itself.
To me, the article seemed to strongly imply — although not explicitly state — that the document was created post hoc to fit the story rather than being genuinely completed at the time of his degree program. They proceed as if the mystery is in how he created the document at the time, rather than to question whether it was created at the time, even though that seems to be an obvious question to raise.
To be clear, I don't mean to suggest Ritchie did fabricate anything — to me the thesis (links to which have posted by someone in this thread) looks very similar to other mathematical documents from that time. But the article is written in this way that seems strange to me, in that they focus on assumed typesetting anomalies rather than all of the assumptions themselves.