If you examine the 2nd screenshot
you'll see the opening and the pod that they are about to attach is like 2/3rd the size of the Mercury capsule.
I've included a comparison image of a 6' person or about the height of Finney who is taller than Kirk next to the TOS-R Ion Pod. The TOS-R Ion Pod's ring or attachment interface to the hull is about 4'3" and the dome diameter is about 3'5". Finney would need to be a contortionist to fit in it.