Everyone is exposing themselves to brain damage thinking about this subject.
Regarding steady speed operation on a 5.7.....a oil relief passage, within the block, is controlled by the ECM.
When all the MDS parameters are met the ECM opens the relief passage allowing all pressurized oil within the 8 lifters related to the MDS cylinders to bleed off.
The lifter base still rises and falls while following the camshaft, but because there is no pressure within the lifter, the piston within the lifter just floats, holding the pushrod in position while lifter rises and falls around it.
All 8 valves are closed and the pistons operate in a pressure/vacuum environment.
Beyond the parasitic drag of rings and bearings the pistons neither contribute to nor cost any measurable power.
At this time the injectors are also shut down and the coils are switched off.
So much for MDS...
Carbureted engines produced huge amounts of unburned hydrocarbon emissions (unburned fuel) because when you took your foot off the throttle and coasted, the vacuum below the closed throttle plate pulled fuel through the idle circuit.
Because the throttle was closed there was not enouph air below the throttle plate to support combustion.
As a result, unburned fuel just passed through the combustion chambers and out the tailpipe.
The worst examples were vehicles with manual transmissions because the RPM could not drop due to the fact the car was now turning the engine, through the clutch. But the automatics were almost as bad as they kept the engine spinning as well.
In the late 60's manufacturers introduced a method to inject a predetermined amount of air into the exaust manifolds, helping to finish burning the unburned fuel being pumped out through the exaust manifolds.
Old car guys know this as a Smog Pump.
It was nothing more than a belt driven low pressure high volume air pump using a diverter valve to meter air into the system and turned out to be quite effective at reducing unburned hydrocarbons throughout the RPM range.
Because it looked like it might cost horsepower....we threw them out by the trainload.
Anyways, control of unburned hydrocarbons at coast has been a engineering nightmare from the time we knew they were a problem.
Electronic fuel injection has just about turned this into a non concern.
Even though the vehicle is turning the engine at speed during coast (foot off throttle...say 60 MPH for example) and the throttle plate is closed, the ECM has shut the injectors off and the engine is nothing more than a big vacuum pump.
As long as the front pump within the trans is turning, it will transfer rotation from the wheels back through the driveshafts, trans, torque converter, and ultimatly the crankshaft.
If you just have to experiment, find a vacant section of road (fat chance) run up to about 60, release throttle and turn key to off. Do not take it out of gear.
Your going to have to guess your speed cause the dash will be dead during this experiment, but at about 30 mph turn the key back to ON (not start).
I haven't done it with my Jeep because....I'm not that inquisitive, but, you likely will find the engine is now running.
You have now manually done what the vehicle does electronically....you shut off the injectors during deceleration and restored the injector operation just as the front pump was loosing its ability to drive the engine due to lowering road speed.
So all that aforementioned B/S that preceeds boils down to is...YES the injectors shut off for a period of time during deceleration.