Gargoyle Stoneplate Clarity and Functionality Issues

Right now, Gargoyle Stoneplate's active is not clear and should be revised. The current active reads:

UNIQUE ACTIVE - METALLICIZE For 4 seconds, grow in size and gain bonus health equal to 40% of your maximum health, but reduce damage dealt by 60%. If Stone Skin is active, the health increase becomes 100% instead.

Although the idea is obviously overpowered, I understood that I would be granted 100% of my health as if the item were a really strong Lulu ult that would leave me with full health after it faded away.

It turns out that the bonus health gained doesn't work like bonus health gained from Lulu's ult. The bonus health gained from the item's active is only temporary, fleeting health with an unexpected side-effect.

Let's say I have 700/1000 HP (70%). According to the item's description above, being near 3+ enemies when activating the active should give me another 1000 HP, turning my health into 1700/2000 HP (85%) if it behaved like a Lulu ult. What actually happens is that the percent health is preserved and the health is changed to 1400/2000 HP (70%).

Now let's pretend that during the next 4 seconds I take 900 damage and my health drops to 500/2000 HP (25%) before the active runs out. Once the active runs out I would expect to keep my bonus health as if I were healed by a Lulu ult. What actually happens is that, once again, the percent health is preserved and my health is then changed to 250/1000 HP (25%). At both activation and deactivation, the passive keeps my percent health constant. Because of the way the activation and deactivation of the item preserve the percent health, the item's active effectively reduces damage received. The 900 damage I received during the 4 second activation of the item was effectively reduced by 50% to 450 damage.

What we have is not an item that grants 40%/100% bonus health, but an item that grants 28%/50% damage reduction for 4 seconds because of the way it grants and takes away the phony bonus health. But the item doesn't just reduce damage received, it reduces any and all changes to health. This means that it also reduces true damage received and healing received.

Gargoyle Stoneplate also has the problem that it messes with health scalings. A notable example is Cho'Gath's ult scaling really well with the bonus health granted and isn't affected by the active's debuff since it's true damage.

If Gargoyle Stoneplate's active were made to grant damage reduction instead of temporary bonus health, instances of true damage and healing during the 4 seconds would work as expected and any health scalings wouldn't be affected.

TL;DR: Gargoyle Stoneplate's active should grant damage reduction instead of temporary bonus health.