The Mac Pro bar isn't quite correct. The last update was only due to Intel not producing the old processors any more. Apple didn't even flag it as "new" on their store.
You might be right, let me look into that. There's a bit of gray area as to what technically constitutes a "release".
Seconding this. The 2012 "update" was no more than a slight rearranging of CPU and RAM within that same generation of parts. The thing still uses all 2010 era parts (radeon 5xxx graphics, westmere xeons, 3gbit SATA, PCI-E 2, no thunderbolt). It has been "due" for an update since sandy bridge xeons were released in early 2012.
Actually they did, briefly. But was probably a mistake.