Well, this threat is about easing the start - and there the wiki will be small. Browser storage has its flaws, but it could help to avoid loosing your first hour of work.
I often taught pupils writing stories in TW (like in Twine which is in fact a TW under the hood), and they thought that their work was saved when clicking the checkbutton of the first edited Tiddler.
It is the questiion whether we want to treat the many cloudnatives, who carelessly log in to every website with their google/apple-id and do not care what is happening in the back, as burnt flesh for a real understanding of computers which TW could provide if they would stick to it.