My recollection is that the bottom right corner of your photo is where the cyclinder tab slides in and out depending on the key position. I think that with the key removed, the tab is "out" which protrudes into the steering column and physically locks the steering wheel; and when you turn the key "on", the tab retracts so as to unlock the wheel. So the procedure is to turn the key off and remove it so the tab protrudes; saw off the tab. Thus the tab will never protrude and never lock the wheel.
(Not sure why the tab is not protruding in your photo with no key...)
Found a before and after photo here at the very bottom of the page:
https://www.rennsportkc.com/spec-boxster-build-part-7/