I do recall the days of audio typing though. That was when people dictated their text into a tape recorder (Dictaphone or whatever). The typist had foot controls to stop and start the tape (a bit like a sewing machine ) That suggested to me that the spoken word was faster than typing.
Another reason could be that sometimes with recordings what has been said is not clear the first time you hear it and you have to listen multiple times to make out some of the words.

Personally I type a lot faster than I can write. This is perhaps because I'm left handed, and my writing sucks; after 2hr exams my hand feels like it's about to fall off!

ac