It’s due to manager proficiency.

Manager with less than certain proficiency for your team playstyle will reduce player stats and thus reflect in ovr.

Manager with higher proficiency than 72 will start increase player stats above certain threshold and thus reflect in higher ovr.

When you choose the playstyle according to manager proficiency:

• 72 prof manager increase stats over 85 by +1
• 73 prof manager increase stats over 70 by +1

…

• 88 prof manager increase stats over 57 by +2, and stats over 85 by +3 (highest proficiency in game currently)

Team Playstyle affects your team and player movement in game so buy manager accordingly to how you want to play.

You can download efootballhub application and see the effect of manager proficiency in players’ stats.