For anyone else momentarily confused by this, they stopped selling the last corded mouse four years ago, but haven't bundled a corded mouse with any computer since 2009 AFAIK. Which makes the comment about "corded mouse they ship with iMacs" feel even older.
Interesting, I could have sworn they were bundling the corded mouse with iMacs circa 2015. Are you sure about your comment about bundling?
In any event, yes I did not know they stopped shipping them but that is only a good thing. I think the polite way to describe the quality of those mice is not very good. Several more impolite terms come to mind.
I'm not certain, but I believe they started shipping the flat magic mouse, er, mice with the 2009 iMacs and 2010 Mac Pros. Unless you only got the magic mouse with an upcharge? That could be the case, although I think it was standard.
I traded my own iMac in a few years ago, but got to keep the peripherals. I'm not a huge fan of the, uh, flat ergonomics, but it is an amazing mouse when you need one to throw in a laptop bag, and the sensors are top notch when it comes to actual tracking. If only it came in a more ergonomic shape...