It’s really not that complicated. The only other direction to go on I-65 is north.

Interstates with odd numbers run north and south. Even numbers run east and west.

Sure, but use Google maps and have a look at “i-435”
And I thought I-45 being an “interstate” that only exists in Texas was bad!
There are interstates in Oahu if that helps, ha ha
Also Alaska and Puerto Rico! The interstate signage is more about the funding source than where the highway actually goes.