My 12" single of "Ipanema" from the B-52s is 3:58. The album version is 4:24.
My 12" single of "I'm So Excited" by the Pointer Sisters is 3:47. The album version is 3:53.
I doubt that'll convince you, either. But I recommend that you actually obtain a 12" disco single from the late 70's and a 45 and compare with your own ears. It's also fun to look at the difference in the grooves with a magnifying glass.
