Quintorius Kand (Vanguard)'s +2 does not trigger Rem Karolus' ability [Investigating]

biosterous

[Rem Karolus, Stalwart Slayer] states "When another source you control deals damage to your opponent's Planeswalker: Deal 2 damage to your opponent's Planeswalker. This effect can trigger up to 3 time(s) per turn."

[Quintorius Kand] (Vanguard support)'s top ability states "Deal 3 damage to the first opposing creature and to your opponent's Planeswalker. Gain 3 life"

Board state: Rem and Quintorius on the board, with nothing in play that will deal damage between the beginning of the player's turn and the player being able to make a swap (ie nothing like [Valakut, the Molten Pinnacle] on the board. Use Quintorius' top ability.

Expected result: Quintorius deals 3 damage to the opponent's Planeswalker, triggering Rem's ability. Rem deals 2 damage to the opponent's Planeswalker.

Actual result: Quintorius deals 3 damage to the opponent's Planeswalker. Rem does not trigger and does not deal damage to the opponent's Planeswalker.