Yep and that's what an A2000 is as well - an A500 in a big box with expansion slots.
Well, in my laymen terms it is anyway!
It was released in order to compete with an A500 conversion unit supplied and sold by Checkmate Digital that was also called the A1500. It was shifting a few units and Commadore thought, "we'll have some of that".
My friend bought the conversion model; hence my laymen terms above, but both the official release and the conversion were essentially the same spec, give or take a few slots.
As for the extra drive, all I can think is that Commadore must have had a lot of spare floppy drives hanging around
Later, an A1500-Delux was released with a rom switcher (1.3/2.04) and a ram expansion. Whooooooo, what a piece of kit!!!!