It is a bad example because when you use git, your local copy is a full repo with the whole history so it not like your code is lost forever if github cancels your account.
It’s a good example because that’s what they’re saying. With GitHub you’re not limited to editing through the web UI. With Figma you are.
Something like Figma backed by data you control would be fine.
@no-privacy's second paragraph is confusingly worded but I think this was the intent of the post - that comparing to Figma to Github is a good/bad example because they're easily differentiable/not alike.
Code is not lost forever, but you lose commenting on commit history, image uploads on comments, issue trackers , etc