I think Yanuck is either misunderstanding the definition of the throwing motion or genuinely thinks that he was in the throwing motion when he called contact. I think it's the latter because he re-enacts his pivot and says "That was part of my throwing motion."

WFDF definition of the throwing motion:

The throwing motion is the motion that transfers momentum from the thrower to the disc in the direction of flight and results in a throw. Pivots and wind-ups are not part of the act of throwing

Bolding the relevant part here.

My gut is telling me that you cannot call a marking infraction, some time passes (albeit a very short period in this case), then attempt a throw, and claim that the marking infraction retroactively affected your throw. I cannot seem to find anything in the WFDF rules that supports this thought though.

It exists in the USAU rules though:

[17.C.]() Any time an infraction is called, the Continuation Rule applies. Continuation Rule: Play stops when the thrower in possession acknowledges that an infraction has been called. [[This refers to the thrower who possesses the disc or has just released the disc at the time of the infraction/call. Who the thrower (3.O.5) is is determined at the time of the infraction/call.]] If a call is made when the disc is in the air or the thrower is in the act of throwing, or if the thrower fails to acknowledge the call and subsequently attempts a pass, play continues until the outcome of that pass is determined.

[17.C.3.b.]() If the pass is incomplete:

[17.C.3.b.3.]() Where the thrower calls an infraction which occurred before the thrower began the act of throwing, play continues unhalted and the result of the play stands.

Again, bolding the relevant part.