Who's talking about stats? We're talking about raw TOI.
McDavid:
D+1: 15 minutes ES, 3 minutes PP, 1 minute PK
D+2: 17 minutes ES, 3 minutes PP, 50 seconds PK
D+3: 17:30 minutes ES, 3 minutes PP, 1:15 minutes PK
Matthews:
D+1: 15 minutes ES, 2:30 minutes PP
D+2: 15:45 minutes ES, 2:15 minutes PP
D+3: 15:55 minutes ES, 2:30 minutes PP
How exactly does McDavid killing penalties for 1 whole minute a game make up for him having 2.5 more minutes TOI at ES and PP?
By Babcock's last full season, Matthews was 33rd among forwards in ES time, 64th in total TOI at 18:33, and a whopping 96th in PP TOI. MacKinnon was a full 2 ES minutes ahead, McDavid almost 3. MacK had a full 1:30 more PP time, McDavid almost a full minute.
Reasonable coaches play their star players in top minutes. Matthews going from unreasonable to reasonable usage does not require a conspiracy to explain. If anything you'd need a Babcock conspiracy to explain why the #1 ES goal scorer in the league was getting blatantly underplayed.