Atmospheric pressure is still lower than the pressure above the check valve(s). Letting a pump start against any pressure lower than the pressure above the bottom check valve, is like letting the train locomotive get up to full speed before hitting a boulder on the tracks. Kind of like firing a rifle with a bullet stuck half way down the barrel. It is not good to have an obstruction half way up the pipe.
The large check valve/small check valve in one thing is not new. Cla-Val has been making check valves and all kinds of valves that way for generations. Anything that solves the problems with VFD's and helps people get use to constant pressure systems instead of thinking their water comes from a tank is a good idea as far as I am concerned. The next step in their evolution is figuring out how to get constant pressure without the complications of VFD.
What makes me "happy" is helping people solve their pump system problems. I could be selling expensive and short lived VFD's instead of inexpensive and long lived valves. I recommend what I think best for each application, and sometimes that even means a VFD.
I just recommended a VFD to someone in Hawaii. They have a 75HP set 900' deep, static at 675', filling a huge above ground storage tank. There is only one check valve at the bottom, and this is an instance where multiple check valves would help. Filling the huge storage tank is basically open flow into the tank. The line goes up and over for an air gap, a probe system turns the pump on and off, and there are no valves of any kind, other that the check valve on the pump. Starting at 250 GPM is no problem as the line into the tank is unobstructed. It would be easier for the pump to start against some restriction, but there is no water hammer on start up as there are no check valves for the flow to crash into. The problem is water hammer on pump stop. With the check valve wide open at 250 GPM when the pump stops, the water reverses a couple inches as the check valve slams. This is the kind of water hammer and check valve failure that is helped with multiple check valves in the line. But only when pumping open flow on the ground or into a storage tank at open flow will multiple check valves not cause water hammer on pump start.
When pumping into a closed system and using a CSV, the pumps flow is reduced from 250 GPM to 5 GPM filling the pressure tank before the pump is shut off. At 5 GPM the check valve down on the pump is only open the thickness of a piece of paper, so there is no slam or water hammer when the pump shuts off. While using multiple check valves can reduce water hammer on pump stop when pumping open flow, they cause tremendous water hammer when starting a pump into a closed system.
The system in Hawaii had no place above ground to install a CSV and convert it into a closed system, They also did not want to barge a rig over there to pull and set and add additional check valves. So I recommended a VFD with a ramp down feature. The VFD was going to be a very expensive option, but should solve the water hammer on pump stop. In an open system, ramping the motor speed down until the pump is only producing 5-10 GPM before shutting the pump off, has basically the same effect as a CSV closing down to 5 GPM in a closed type system.
I think the idea of multiple check valves still hangs on from the old hydro-pneumatic tank days. Pumping into a hydro tank is basically the same as an atmospheric storage tank as there is no obstruction. The water only hits a cushion of air in the tank. With the bleeder system there is even a cushion of air between the upper check and bleeder. It is different in a closed system with a bladder tank teed off to the side. There is no cushion of air for the water to hit when the pump starts.