The HE-4 is basically an HE-5 LE with the magnetic structure on the backside of the transducer only. The HE-5 LE has got magnets on both sides of the driver. Thus the allegory to Single Ended is confusing if you have not held both units in your hands. It would be even more confusing if it said the "one sided version".
That said they do indeed differ in sound with more control and definition in favour for the HE-5 LE. The HE-4 is really good for less well recorded material and in Gemany there are a few Metal Afficionados who really like what the HE-4 does for them.
So if you always wondered why the HE-4 is lighter and has got a lower sensitivity: It is missing half the magnets of its bigger brother.
If you wanted to you can run either unit unit with a balanced mode as the mini-coax connectors allow you to build your own cable.
Jan