The A2 axles had several design differences from the A0/A1 axles. Some were due to the CTIS system and some were not. Why not make the tire company that damaged it put the new one on to ease the pain?
As far as the Parts TM, I see where they only show a 2 piece shield like you mention. While the top and bottom are numbered differently, both numbers show the same part number and NSN. Searching with the NSN, there were a couple that showed up on Google and the pictures showed them being one piece shields so who knows. I didn't dig through the whole TM for it but I didn't see anything to differentiate between the 1 piece and 2 piece shields as far as part numbers go. I have seen pairs of the 2 piece shields sold on Ebay a while ago but don't see them now and don't remember the NSN they were listed under. I don't deal with much A2 specific stuff so I might be missing something...