I've been hanging around on the mailing list for a while, and it's clear to me that there has been very little work going on in Io in past months. (E.g.: There are obvious bugs in the Range addon that they've known about for as long as I've been using Io.) I'd be very doubtful that we've seen any performance increases, even small ones.
The vector benchmarks show off the sort of code you wouldn't really write with Io anyway, are three years old, against Python three versions ago.
You're right that Bini doesn't seem to care about performance here, and that's fine. But it's certainly a huge problem for Io, obvious even in small scripts, that would be reason enough to fork it.