Our Dodeca architect, Amy, was having problems with the classic Excel add-in (v220.127.116.11) on her laptop and so I took a look. I decided to look to see if the problem as a rogue copy of the xll file on here systems so I did a search for all of the xll's on her system. Here is what I found:
There are 28 localized versions installed by default. No wonder people are complaining about the size of the download. I didn't check to see but I would guess each of these directories contains a full client (localized) API which would be huge.
I hear they are planning improvements for 11.1.2. For the sake of those still on the classic add-in, I hope so.