I believe Shimano started referring to their RD pulleys as "units" (e.g., including bushings/bearings and covers) and giving the unit a single PN - vice giving separate PNs to each small part (e.g., pulley, bushing/bearing, cover) - sometime in the late 1980s or early 1990s. That was well over 30 years ago, so initially I didn't think I needed to specify that I was talking about a "pulley unit" vice a pulley less bushing and covers.

Because you appeared to be nitpicking and/or obfuscating. But on the off chance that you actually didn't realize the pulley units on this RD were in fact different items I also decided to be more precise, using Shimano's own terms from their documentation. That also appeared to me to be possible, since you had clearly stated initially that an XTR RD-M952 has "jockey wheels" that are identical. (You've since edited your first comment above to remove this claim, but the original language of your claim is preserved above where I quoted it when first replying to you.)

Thank you for finally agreeing with me that the two pulley units in question on the RD-M952 are indeed different parts and are not "identical" - as you originally stated.

I wouldn't be so sure about that last point; see below.

Apparently it's been explored empirically by the OP in his particular case, and in his particular case it does in fact appear to have made a difference.

But hey: believe whatever you want to believe. I'm done with this discussion.