Before entering the VR capsule both parties had been told the official rules by the organisers and both had agreed to them. They were allowed to wear whatever beast equipment they wished. The only beast weapon they were to use had to be a blade of some type.
Both of the blades that would be used would be of the same tier level. Since it was VR, Quinn was able to select a suitable weapon for himself but just chose to go for a standard longsword.
However, the rules had never mentioned anything about abilities and this was because Longblade had one that would give him a huge advantage in this type of match. Since his skills with a sword were usually enough to win over his enemy he didn't really abuse it, but this fight was one he just had to win.