One long stretch one way and not as long the other

[amroad17]

This interchange here also qualifies for "exiting to stay on the route you are on" as I-64 seems to be the mainline and I-75 enters/leaves even though the exit number is I-75's.

Not really. This is a true split, and I-75 was built and in use for many years before I-64. I remember traveling north on I-75 toward Cincinnati sometime before 1967 (because my dad had a '57 Chevy that we took on that trip, and we would have been in his new '67 Chevy if it was then or after) and I-64 wasn't built until 1971.

I know, but the finished product looks as if I-64 is the mainline at this interchange.

I would have loved to see what this looked like before 1971!  Did I-75 simply curve at the interchange or was I-75 built the way it is now with the future provision for I-64 extending westward?