Mid year 273 in 64 Darts?

Just like the Mustang in 64. They both started mid year. I had clowns tell me I could not have a 64 Barracuda or my brother could not have a 64 Mustang convertible. Just ignorant or bad information. Not worth your time.
For several years now I’ve heard many people call some ‘65 mustangs 64 1/2. I never heard such a thing in the sixties or seventies. I had a ‘65 mustang that was built April ‘64. The car had a generator, not an alternator. It also had a road draft tube instead of the pcv system. Titled as a ‘65. It kinda bugs me hearing ‘64 1/2.
Jerry