I don't think it's mechanically possible in the 870.
Assuming you have one round inside the receiver laying on top of the shell lifer and more shells in the magazine, the gun would jam when you tried to operate the action.
As the pump handle is pulled back the bolt opens and a shell is fed from the magazine into the receiver and on top of the shell lifter.
With a shell already in the receiver, the gun would jam when the shell in the receiver blocked the shell attempting to be fed.
With one shell in the receiver and the next shell jammed partially out of the magazine, the action couldn't operate the shell lifter to feed the first round.
Then too it takes much more force to operate an 870 fitted with the flex-tab feature with a jammed shell.
Contrary to popular belief, the flex-tab cut in the shell lifter isn't so you can use a pocket knife to push the shell back into the magazine, it's so the slotted tab in the lifter can flex and allow the bolt to over ride the shell and open so it can be fed normally.
To use this feature if a shell is trapped in the receiver, all the operator has to do is pull harder on the pump handle to force the action open.
This does take more force to operate the gun.