As stated in the Tournament Help (linked below - accessed on the Tournaments page), unless stated otherwise the scores don't reset - so you are correct, for this tournament scores are cumulative through rounds 1-3, and then in the round description you can see that there is a "Score Reset" each round thereafter, effectively making it an elimination bracket after that point.
http://www.conquerclub.com/public.php?mode=tournaments5
Scoring
By default scoring is based on number of Game Wins over the entire tournament. However, individual Rounds may Reset the scores, so that the scoring will begin again from that round. When the first round of the Tournament is seeded by score, the player's score at time of joining the tournament is used in that round only.
Ties in Score shall be broken by the following rules, applied in order:
Percentage of wins in the tournament as a whole
The cumulative number of Game rounds required to win the games they have won in the tournament (winning in less rounds is better)
The order in which the player joined the tournament (first player to join wins)
Round Details
Round 1: Seeded by Score, 5 Games, 32 Move On, Games: 2 Players, Standard, New World More
Round 2: 32 Start, Random Draw, 5 Games, 32 Move On, Games: 2 Players, Polymorphic, New World More
Round 3: 32 Start, Random Draw, 5 Games, 16 Move On, Games: 2 Players, Polymorphic, New World More
Round 4: 16 Start, Score Resets, Seeded by Score, Best Of 7, 8 Move On, Games: 2 Players, Standard, Escalating, New World More
Round 5: 8 Start, Score Resets, Seeded by Score, Best Of 9, 4 Move On, Games: 2 Players, Standard, Escalating, New World More
Round 6: 4 Start, Score Resets, Seeded by Score, Best Of 11, 2 Move On, Games: 2 Players, Standard, Escalating, New World More
Round 7: 2 Start, Score Resets, Seeded by Score, Best Of 15, Games: 2 Players, Standard, Escalating, New World More