Yes, they work.
The fastest way for me to test bedding is to grasp the stock wrist in one hand and smack the barrel with the heel of my other hand and then listen. The barrel and stock should resonate like a tuning fork for a second.
The way they work is:
1) The steel bedding block is fastened to the stock with a good area of epoxy.
2) The barreled action from above and the trigger guard from below clamp the steel block.
3) This way a low compliance fastening occurs between the barrelled action and stock mass so that over the recoil time period of 25 ms, they react as one mass.
The barreled action contacts from above via the flat part of the bottom of the recoil lug.
The trigger guard contacts from below via the orifice of the front pillar.
The advantage is that any Mauser barrelled action can drop in and have a perfect fit.
The disadvantage is some commercial Mausers are cast, and the bottom of the recoil lug is crude and rough. I have turned some commercial Mauser actions upside down in the mill and flattened out the bottom of the recoil lug.
I have built this same type of system, but different dimensions, for Mosin Nagants. They vary in the angle of the back of the recoil lug. I mill the back of the recoil lug square. Any Mosin would drop in that has been milled, but I am the only one doing that, so almost none