League of Legends Reforged Rune: Grasp of the Undying

Lol wiki says: “Entering combat generates 1 stack every second for the next 3 seconds. Additional stacks may be generated by re-entering combat after 2 seconds. After reaching 4 stacks, your next basic attack on-hit within 6 seconds against an enemy Champion icon.png champion consumes all stacks to deal ( Melee role.png 4% / Ranged role.png 2.4%) of your maximum health as Magic damage.png bonus magic damage, Heal power icon.png heal for ( Melee role.png 2% / Ranged role.png 1.2%) of your Health icon.png maximum health, and permanently grant ( Melee role.png 5 / Ranged role.png 3) bonus health. The empowered attack duration refreshes whenever going in combat.”

So according to lol wiki grasp of the undying requires players to leave combat and then re-enter in order to gain the last stack to proc the rune. Is that really the case?

So, if I throw poppy’s shield, it still gives me 5 health instead of just 3 now?