If they were more skilled, they would have won 11 the first day and 9 the second day. If they were less skilled, they would have won 9 the first day and 11 the second day.
But the performance you would see would be more than what the game can track. The game can’t track call outs, zoning or target prioritization.
Probably both. People’s performance absolutely does vary from day to day.
Your personal performance is the one common denominator across those end results.