Savage did make a few action for the WSM and RUM with the small shank before moving up to the large shank. Im not 100% sure of this action start to weather or not it started out as the RUM.
The Thought that the small shank Savage action is to weak for the RUM's is ridiculus , think about it the Rem is 1.062"x16 TPI and the Savage is 1.055"x20TPI , ok now thats only .007" differance and that makes the Savage thicker walled before you even factor in that the threads on the Rem are ALOT deaper than the Savage and that thins the Rem out even more so in reality the Savage action would be stronger , the trouble lies when the actionis setup with the barrel nut because the barrel's max diameter around the chamber is only 1.055" instead of 1.250 like the Rem. So if you set the Savage up like the Rem and have a 1.250" shouldered barrel setup its actualy a stronger action. The Bolt head on a Savage is investment casted , and alot of foks shy away from them because of that but ask anybody who has ever cut a Savage bolt head they are WAY harder than the Rem 700's and the lugs are also a good bit thicker. If I had to put money of the stronger of the two actions having them both barreled the same I'd bet on the Savage.
This action can be built into a RUM or a Lapua just as well as a Rem 700 , you won't get as many after market parts for it but it can be had for $125 less also.
Anybody who buys this action has the option to get a sweet deal on a good 30 cal barrel also.