Here's some datalogs illustrating what's going on. This is a lap at WSIR (available in Gran Turismo 6) that shows the RPM plot, throttle position plot, and clutch position (on/off switch).
Now, lets zoom into that spike with the peak RPMs.
You can see clearly between the 2nd and 3rd graph, that I am COMPLETELY off throttle, before the clutch sensor is engaged. However, being an on-off switch, you can't see the exact position of the clutch.
Between 1.00.46 and 1:00.56, there is a surge of 554 RPMs, which occured from a WOT shift at 7209 RPMs.
As you can see from the first, zoomed out graph, there are a LOT of RPM surges at WOT shifts, which happens with any FI solution. You'll also note that all of my shifts, except for that one, occur at 7000 RPMs.
This wasn't even a record lap attempt at WSIR. You can imagine the RPMs with a 7850 redline...