BMW is increasingly combining parts as soon as they are even remotely interchangeable, in order to reduce stock levels. Nice cost savings perhaps, but also extremely risky as parts may be very different and hard to combine with other parts. For example, if you break a front spring on an E30 M3, the replacement BMW will send you is from an E30 316. You can imagine what that will look and handle like on that car! So sadly the information in recent versions of BMW's ETK (and bmwfans, realoem and the likes use that as a basis) may vary from what was done by BMW back in the day!
I sincerely believe they should implement this in another way, like mention what part was fitted originally, and what is a suggested replacement so you are alerted and can check for yourself. Now in most cases you won't even know before you run into issues! Sadly BMW's ETK had no provisions to implement the new approach in a better way but you have to be very, very careful!
So in other words: current documentation may say that certain parts are fitted, or that they are the same as from many other models, but that may not be true! It may have been completely different back in the day.
Want another example? According to ETK and BMWFans all facelift E21 front struts are the same...
