Auto Increment Function Broken (revived issue)

I think there is something wrong with the forum software. I've actually posted an update to my first version of this issue (MDEV-29416) and I now have 2 open issues, neither of which appear when I try to select my open issues. Given that, if valid, this is a pretty serious bug, I'm guessing that the potential forum failure is why no one who was watching the issue has reponded to my update. Hence I'm re-raising it here.

The detail is in that previous issue. Short version: uploading a CSV file with 10k rows into a virgin table with autoincrement should result in the final autoinc value at 10001. In my scenario, It doesn't. It consistently arrives at 16384. (with 2 different versions of the server, 10.8 and a freshily installed 10.9.3) It is not data dependent. Any of the hundreds of CSV files I've created produces the same result.

I was asked to provide the means of recreating the issue and the attached zip file contains the 5 files required, including a short note giving precise instructions on how to recreate it.