Ok – it looks like there’s a fix for this (glad it’s an easy one):
Go to your Contact form admin page – at the top, there are now two snippets of code – a new snippet and an old snippet. Chances are your page is still using the old snippet. When I copied the new snippet, pasted it into my contact page, and tested a submission, I received only one notification email.
Hope this helps anyone else facing the same issue. Chaos, let us know if it worked for you!