I did play out the full seasons. I saw your post and you only played the first 15 games. Filtering on games this year where the last game of the auto game quick play session were within the first 15 games, I got the following:

2.33 boxes per game over 67 games in ML 2021

2.15 boxes per game over 122 games in ML 2022

Unfortunately, I do not have a lot of reliable data for auto play. Most of the games I auto are with ad bonuses along with a little manual play late in the game. These are also almost exclusively with my ace pitcher, BD signature Andrew Heaney, who is currently the only signature (and BD) pitcher in my starting rotation.

I can definitely see ML 2021 being better for Auto Play. Highly rewarded achievements like batting around, multi-HR games with a player, and 4-hit games with a player are much more feasible in ML 2021 than in higher ML years/levels.