Having watched the 'Youtube' video on the Broncos site, I reckon Soward took exception to Greg's slightly late (but with both hands raised) challenge. He then appears to tackle Worthington from behind. I can't actually see any punches thrown by either player but Ben Thaler obviously did - he's right in the middle of the melee. So, presumably the referee's report has been used here, rather than an inconclusive camera angle. I still believe Thaler is the best there is, and am prepared to trust him on this one.
OK, we can argue that, if Soward hadn't tackled Greg, nothing else would have happened. Or we could argue that, if Greg hadn't gone in recklessly on Soward, nothing would have happened. As the EGP is available to both, it looks like no suspension for Soward, and three for Greg.
In some ways, we could benefit from this decision, as we have cover for Worthington, and I'd prefer Soward to be available for the Broncos against the rest of the teams!