I also had a same situation.
I attacked Heart of Kiran with +1/+1 counter by Basri Ket. Kutzil Crewded.
At the same time, my Toski was atttacking. It trrigered and I could draw 3.
But Kutzil's ability didn't trigger.
I had a Raffine's Informant with a +1/+1 counter on it attach with the Kutzil, without a +1/+1 coutner, and I didn't draw a card. The previous turn I attacked with the Informant alone and drew the card.
Match #263635529 Game #857766980
Also experienced this. Had an Ironpaw Aspirant with its counter on it attack the turn Kutzil was cast and deal damage - trigger happened and drew card. Next turn, attacked with ASpirant and Kutzil, damage - no trigger, no card draw. Cast Malamet Scythe end of oppo turn, attach to Kutzil. Next turn attack with both, damage, trigger happens, draw card. Match 263650327 Game 857824046