I think you’re missing my point. Just because it isn’t THE AMG widebody, doesn’t mean it wasn’t done by AMG. I’m not saying it was done by them, I’m saying you can’t be 100% sure it wasn’t.
I don’t know what you’re picturing, but there was no AMG factory in Japan or the UK, and car’s certainly didn’t get sent half way around the world for a bit of bodywork. Engines were sometimes sent from the UK/Europe, but I’m not sure about Japan.
AMG parts were sold by dealers, each dealer had a workshop either with a paint shop or one close by. There was a shopping list of what’s available. People came in, ordered it, and the dealer fitted. There were many dealers all around each country, all of which did whatever the customer wanted.
If we were talking about this car instead, you’d be arguing it wasn’t done by AMG because it doesn’t have the proper arches, but it was. So why didn’t they fit them?
AMG never sold manual cars most people say (even AMG) but they’re out there on 1 owner cars, same for brake upgrades etc. It was all bespoke. You could have as much or as little as possible.
Just because a shop sells Recaros in Japan I don’t see how that means they were fitted recently. They look a bit worn to be recent. Most of this stuff wasn’t documented. Yes they’re clearly not the proper arches, but you can’t be sure the proper ones were the only type every possible dealer ever fitted to every car they have ever worked on in Japan, ever.
There is no proof either way, but there is a lot of proof AMG did things that weren’t in the brochures.