Well it looks as if they are still working on it, because I've got 15.17, and the scrolling is, if anything, worse.
One thing that did occur to me is that keyboard repeat rate could be a factor, and after some experimentation it looks as if the scrolling behaves properly with a slow keyboard repeat rate. (I've no idea which setting is the default; I've always just set
it to the fastest one.) Perhaps this is what the Excel developers have been testing with, and another row needs adding to their test checklist...
I've sent them (yet) another sad face bug report, this time pointing out that perhaps they need to tweak the keyboard repeat rate to see the problem. So we shall see.
--Tom