I’m not sure if there is an agreement between the AFL and Epworth about players going there as a matter of course (although doctors and physios wear Epworth branded clothing on game day). Ultimately the call would be by the paramedics if they felt he had injuries requiring care in a trauma centre but the main cause of issues here (the spleen injury) is not easily diagnosed without CT scanning (which can show both the injury and evidence that active bleeding is occurring). No referral is needed to go to an emergency department.
An analogy I would use here is having someone fall off a ladder at home and be taken to a local hospital where it is discovered the injuries are worse than realized and they are transferred to a bigger centre. Most tertiary centres in Melbourne would have capacity to perform embolization (causing the vessels to stop bleeding using a catheter in the atery) of a bleeding spleen after hours and this is probably the main reason he was transferred (he could have had his spleen removed at Epworth but would then have had a major surgery and need additional precautions to avoid infection in the future).
Calling patients family members is an absolutely standard element of care after a procedure. This may have been scary for them to receive but to not call would have been poor in a communication sense.