Nobody should purchase this specific ship with the belief that she is immune to potential future nerfs. I agree that a nerf to Yamato does seem unlikely at this point, but WG’s advertising clearly indicates they have decided they will nerf ARP Yamato if deemed necessary. If ARP Yamato was immune to nerfs, why would WG add this disclaimer to this ship, when it is present on no other ship in the game (tech tree clone or otherwise)? The thing that makes this ship different from all others is that she is a special ship that happens to be available for doubloons, but WG’s stance on balancing special ships isn’t necessarily relevant in this specific case anyways. I suspect if there was a sudden, pending need to nerf Yamato (and let's be honest, I doubt very much that would ever happen short of a huge change in mechanics), ARP Yamato might end up archiving such behaviour as a dinosaur. Going against the theory of ARP Yamato ever being nerfed are the retiring of both HMS Thunderer and Smaland.

She was hit with a nerf to her armour plating, though this could be argued as just being part of the blanket HE / IFHE changes which hit all sorts of premium ships too.

It's not like Wargaming jumped at nerfing problem special ships when they arose either.

They're simply being retired without first attempting to curtail their problem performance. We've never seen them adapt to a specific targeted nerf. Like I said, we've only ever seen clones buffed to keep pace with their tech tree counterparts. It still remains to be seen if they'll end up as dinosaurs if Kongo or Myoko were changed. The ARP Kongos and Myokos only gained those premium protections belatedly.

The ARP Kongos and Myokos are premium ships, though.

Yamato review world of warships