Chadwick was ranked 154th by Central scouting so somewhat below Nielsen (who still wasn't ranked in the top 100). At least he was taken around where he was rated.
The WHL players taken between 2016 and 2020 would have been mostly Derkatch people with maybe some Speltz in there because DD came in summer 2015 and Speltz the summer of 2016. Garth Malarchuk was also a western scout and may have have brought them Neilsen and probably Valiev in 2014. I am not sure how he and Derkatch divided the Dub.
Derkatch left after the 2021 draft so Lisowski. Chadwick and Malinoski are not his. Maybe Malarchuk again? Based on the western draftees I don't see the allure of Malarchuk but it is certainly possible that the players he contributed to the annual lists were later found to be good choices but just not there when the club selected.
About Chadwick he was a big offensive producer before coming to the WHL so this year would not be a complete surprise, and his draft year lack of offense would not be the reason he was a 6th round choice. Hopefully whatever else he was lacking matured with the offense. Skills with the puck were not all that he was missing.