You do realize Heiskanen, who is a year younger is currently putting up better numbers right.
The other thing is, how many elite Finnish defenders have their been, and how many of them played in SM-Liiga at 19? Ristolainen came over immediately. Your basically left with Vatanen had a higher PPG at 19, and the same one Juolevi currently has as a 18 year old. Here's a full list of U-20 defenders and their scoring in the Liiga.
Eliteprospects.com - All-Time Stats and Leaders from Liiga
There are currently 6 active NHL defenders from Finland. Vatanen, Ristolainen, Nutivaara, Esa Lindell and Julius Honka. Of those, only Vatanen, Nutivaara, and Esa Lindell played in SM-Liiga at 19.