Why? It's the same X58 board. Same everything as 5,1. Even if they did something boneheaded like change some text in the model ID. What would you want new firmware to accomplish? Any 2010-201x with 5,1 firmware can use the last greatest LGA1366 available. Nothing beyond that because, you know, socket changed. Probably they call them 5,2.
4,1 use same board with 5,1 right? Why early snow leopard 5,1 boot 64 bit by default but not on 4,1. I expect something like that.
Ok! I known there're no different in the hardware support between 2010 and 2012, But in the future. May be there are something apple serve different. As i suggest you. 64-bit kernel default on 5,1.Again. They are the exact same. 2010 is the exact same as 2012. No change. 4,1 was X58 but needed to have a flash so they could use Westmere. At 5,1 you again have X58 but already can use Westmere. The 2012 offers...X58 and Westmere. Westmere was the last LGA1366 processor branding. I bet you can install 10.6.8 on them as well if that is where you are going with this? If not it would be artificially stoopid on Apples part as most enterprises still use 10.6.8. Because it is superior in every way for desktop use.
Mac Pros are the only Macs left without Internet Recovery built in. Maybe a 5,2 will include that?