As someone who has been using a similar strategy for personal notes (namely: notes as plain markdown files in a folder), I agree with some of the strengths mentioned, but also have several issues.

On the pro side, plain text will always be future-proof and basically king of platform independence. Coupling this to Git(Hub) gives you a backup of sorts, access when you are not on your main device, and cross-device syncing.

In my experience, however, several of these are overrated or unused (at least for my own use cases, but I suspect others', too). There are also many missing features. A random list: I don't really need markdown rendering, find the edit workflow of GitHub to be painful for one-liner changes, miss auto-save, find the search feature slow compared to local searches in editors, and if we're talking about a real wiki: I _really_ miss being able to paste screenshots from clipboard as an unnamed / temporary file.

So then, the question is, why bother with GitHub, and not just do this locally with VsCode / Vim / Emacs / editor of choice? And I would basically agree, and the Git/GitHub part can be added as a secondary feature. However, the article seems to be touting this part well above the rest, and my experience is quite the opposite - you rarely end up using those, or _want to_ use those.