The interpretation for 12.9 says this:
"When making a play at a disc, players need to ensure that they will not cause non incidental contact with another player (neither their stationary position, nor their expected position based on their established speed and direction), before, during or after the attempt at the disc."
And the interpretation for 17.8.1 says this:
"If two players have the same space reserved at the same time and contact occurs, whoever caused the conflict of reservations (i.e. whoever last moved so that their reserved space clashed with the other players reserved space - usually the player who got the reservation last) is guilty of the foul."
As far as I can tell from this video, the defender's attack on the disc was always going to lead to significant contact based on the receiver's speed and direction, hence it should not be treated as a clean intercept.
If the defender has changed his direction late, thus "reserving the space last", it should be a foul on him, as he has come into a reserved space and created contact. If not, it should be treated as an offsetting foul, with both players moving to the same space.
"17.10.2. Non incidental contact that occurs as two or more opposing players move towards a single point simultaneously should be treated as offsetting fouls."
As Rueben has pointed out on
: "At its basic level, Ultimate is a non-contact sport that has a bias towards the offence. In these sorts of incidents where contact occurs as two players converge on the same spot, the majority of outcomes will result in the offense retaining possession (either via the receiver or the disc being returned to the thrower). If this sort of collision did result in a turnover, then the rules would be rewarding dangerous play and would be in direct contradiction of one of the basic rules - that Ultimate is a non contact sport.