His explanation is utter nonsense.
An arrow shot straight will hit the ground before it reaches 200 yards.
If the target is relatively close to the archer, then either the archer can shoot directly at the target (but still aiming up so that the arrow reaches them - you understand that an arrow starts to drop the instant it leaves the bow), or they can shoot in a high parabola.
Either way the arrow will hit with a very similar force (actually we should talk of momentum here, not force). Arrows shot high hit the ground with an impressive thump, shot along the ground they tend to skip and may give the impression they have less momentum. It's just an impression.
I am not an expert in war archery at all but I seriously doubt his explanation for another reason. Consider a group charging archers. The archers shoot in a high parabola, the arrows come down near vertically. What is the chance of hitting a target? Now consider them shooting 'directly' at the target. If they miss someone at the front of the group, the arrow might hit someone further back.
Some misunderstanding can happen because arrows shot at distant targets have lessened the amount the shaft is snaking - when they hit the arrow is less inclined to snap and the laws of mechanics say more of the total momentum in the arrow will be used in penetration (due to the arrow shaft not bending as much under impact). If you shoot a high parabola, the arrow path is longer, it has longer for the shaft to settle down.
I've seen this myself when testing penetration on oil drums. Shoot arrow at oildrum 10yards away, shaft shatters, incomplete penetration. Hit same oildrum with similar arrow from 50 yards and there is complete penetration, arrow survives intact.