Heading towards CIS-2020.

It's precisely important which pattern the marking follows. In the case of five patterns, the coin toss gives one player an advantage right from the start.
In the case of six patterns and the marking I described, it’s even unclear who benefits more – the first or the second player. As you correctly pointed out, one marks three, but the other marks last and decides how the game ends.
The specified marking with 6 patterns is clearly more balanced than the marking with 5, where the coin toss indeed gives a clear advantage to the second marker.

I had three more points.