This type of battery shouldn't have a memory problem like Ncads did. I haven't graphed the discharge rate for DJI batteries, but I would think after being half discharged that the voltage might drop below the set point, somewhat quickly. It depends on what the lowest usuable voltage is, your flying activity and how fast the voltage drops after reaching 50%. But, memory like problems can develop in almost all rechargeable batteries, to some extent.
Have you read the real manual? There is something, in there, about fully discharging a battery. The batteries should be stored with a full charge. I tend to think the full discharge treatment was for certain symptoms after a long storage.
It won't hurt anything to fully discharge your batteries and it very well might fix the problem.
How quickly does it drop after falling to 50%? (No pun intended, but it would have been a good one!)