Anyone know which manuscript Glenn Gould's recording of Contrapunctus XIV is based on?

[His recording](https://youtu.be/CpnfQntMisc?si=NekqfHD2ch3oaH-7) ends on this minor 6th leaping from A to F, which I can't seem to find exactly in the various sheet music versions on IMLSP. I'm wondering where he got this from or of this was a just something he did 'cause he liked it.. which would seem fitting.