I think it was probably a borderline decision under the new rules . . . the horse had already been fractious in the stalls before that incident and it did take the stewards quite a few minutes to make a decision.
In this last incident the horse began to rear fractionally before the gates began to open and if you look at the jockeys legs when they become visible it looks as though he is already out of the irons . . . it may even had been a reflex reaction when he initially felt the horse going, especially as he had played up previously.
I can see why there may be a debate under the new rules, the saving grace this time is there was no impact on betting as it was a 16/1 shot.