The difference is Burt had the ball and was always going to score, Gibbs never had to commit to the dive. Hayne was chasing after a ball kicked ahead and dived in at the same time an Goodwin but was beaten. Both guys lead with the knees and were rightly charged but Gibbs was given a Grade 2 because he had ample time to pull out while Hayne didn't and thus was charged with a Grade 1. Hayne missed 0 weeks because of he had no carry over points but Gibbs had carry over points and contested it (no early plea downgrade).
If we look at Merrit who copped 1 week for studding Reddy in the face as he was planting the ball it pretty reasonable. Merrit lead with his feet (Hayne didn't thus not as bad) and he kicked Reddy in the face in the process causing a break in the skin. There have been 10 charges for similar offenses only 2 leading to suspension (Gibbs and Merrit) so I think it is not only the correct ruling but they are consistent. While 3 weeks for Gibbs is harsh penalty I think the chose the correct grading but Gibbs history blew out the penalty.
The Keating charge was all wrong, no intent and was simply trying to make a tackle and the bloke fell during it. I think he was charged only because of the scrutiny and it being a GF next week. Had this happened 3 weeks ago he does not get charged IMO.
yes, there are other differences with gibbs of course.
i'm not convinced he didn't have time to pull out either and he most certainly dived after goodwin. he could have stayed on his feet and jumped over the player or if he insisted on going down he could have led with his upper body.
if hayne's is a grade 1 there are going to be a lot of incidents not as bad as his now forced to be graded as grade 1. for example, the exact same thing as hayne did, but contact is with the back or side. IMO contact with the head, and heavy contact at that, should have ensured it was at least a grade 2.
also, why he and gibbs were not charged with dropping knees i dont know. what is that charge for then? they are completely different offences to the dangerous contact feet first offences slater style.