I went back in this history for this thread and found
@highfivezoom mentioned part number
PYZ3-02-300D was installed by the dealer for his replacement. In another thread from another forum, I found
PYY7-02-300L listed as the part used. When I looked up those parts, the 300L shows as the part number for a '16-'17 CX-9, and the 300D shows for '19+, but I can't seem to find details for what this part really is. Searches take me to various mazda parts sites, but they all just say "Engine Partial" or something like that.
Additional notes:
PYZ3-02-300D indicates that it replaces PYZ3-02-300, PYZ3-02-300A, PYZ3-02-300B, PYZ3-02-300C, so they're on the fifth revision of this part.
PYY7-02-300L indicates that it replaces PYY7-02-300B, PYY7-02-300D, PYY7-02-300E, PYY7-02-300F, PYY7-02-300G, PYY7-02-300H, PYY7-02-300J, PYY7-02-300K, thus making the ninth revision (at least, since some letters are skipped).
I don't know how to find the differences between the revisions, and I wouldn't be surprised if it's locked somewhere in Mazda's own repositories and we're left speculating what was done.
When I called my dealer and asked, they told me they're replacing the short block but didn't give me a part number. The repair with the 300L part had their invoice that stated they replaced the long block, so when I finally get my invoice from this, we may end up with a new slew of part numbers to add to this bag.