This card shares common design elements with "Perfect Machine King" and supplements its vulnerability to being destroyed, so it's likely that this card was made to support it. They were also released in the same pack—Rise of Destiny—and have adjacent numbers.
Their Japanese names, "Heavy Weapon" and "Heavy Armor" respectively, make it clear that "Platform" is focused on strengthening the equipped monster while "Armor" is focused on protecting it.
This was the first Union monster to destroy itself when the equipped monster would be destroyed by card effects (in addition to destroying itself instead of the equipped monster being destroyed by battle). This effect has now been added to even older Union monsters, such as "Y-Dragon Head".
This is one of the few Union monsters that can equip itself to another copy of itself.