String Trimmers

I have a Husqvarna 32xLDX trimmer. I'm interested in purchasing a sweeper attachment (SR600) and my friend has a 324 L trimmer as well, and dropped off his sweeper for me to try. The depth of the input shaft on his sweeper was a good 1/2 deeper than the input shaft on my existing trimmer head, and after locking the sweeper attachment onto my trimmer, my output shaft would just spin and not drive the sweeper; it never coupled up.

I'd like to buy a new sweeper and my next step is to look at the new sweeper's input shaft and test it, but I thought all the attachments should be the same?? See attached photo for the two... my trimmer attachment went back on and worked perfectly like it always had. Thanks.