So the simple part is that the Dark Prince's normal attack is a forward splash while the charge is a 360 splash like the valkyrie
Well if you look at these 2 pictures on the normal and charge attack the splash area is not different it is the same splash so how does can dark prince can do a 360-degree splash if his area splash is the same for both attacks?
Well, what we know is when the Dark Prince does his charge attack it happens almost immediately but the Dark Prince's normal attack animation takes about 0.35 seconds.
Troops which spawn more than 1 usually spawns in tight packs like the Barbarians above. What we also know is that when 2 hit boxes touch each other they repel each other very fast so it does not look like the Dark Prince is going through the barbarians.
After knowing this the reason why the Dark Prince charge strike is a 360-splash even though it's area splash is the same is because when the dark prince attacks use his charge attack the splash area of the Dark Prince's splash plus his immediate charge attack will hit all the 4 barbarians because the barbarian's hitbox deployed on the dark prince's hitbox does not have enough time to repel each other which is about 0.1 sec
Since the Normal attack animation takes 0.35 seconds to initiate the barbarian's hitbox can easily repel the Dark Prince's hitbox before the attack animation finishes causing only 1-2 barbarians to get damage by his regular attack
The reason why the Dark Prince's charge strike can do a 360-degree splash is because of it's immediate attack animation in the Dark Prince's charge state. So technically if you zap the Dark Prince and then let him move again but not enough to do a charge his splash may be a 360-splash but I haven't tested that out yet.
P.S No rude comments lets have a nice civil conversation in the comments
Credits to Orange Juice Gaming for the videos that I screen shot