I have the same problem.
I am not referring to the sorting. I am referring to the fact that the web client beta, and for what I know, also the Windows Beta, sometimes change the create date to the update date for unknown reasons. I cannot reproduce it. But it happens, and I know because I always sort by create date. So suddenly, an old note I touched/edited turns up on top.
I think I reported it as beta feedback for Windows Beta 6.14. It happened to me with the web editor beta again today.