I give the answer to his question mainly in the 2nd paragraph though which starts with "In general you can say that".
I started duel when they were 15 minutes and learned around that 10 minutes was a huge change because its a 30 percent reduction in gameplay time
Any time length will give exactly the same chances to win for anyone
Both of the players will still make the same amount of percentage of good decisions.
Longer amount of time can produce more accurate statistical values of players skill level, win-rates, their decision making and so on,
but it's impossible to predict and assume which of the players are going to perform better or worse given any amount of time.
Perhaps they may need more time to adapt to the opponent, based on their play-style and unique traits which could possibly be more suitable to win more matches if they had more time to adapt their opponents and how they play a particular map at that day and time, just as an example.