HS is notorious for opening earlier than posted park opening. I think if you head straight I slinky you will be good. We did just that and walked straight on even though it said it was already a 30 min wait. Everyone is running to smugglers run at park opening.
We went for Star Wars stuff Dec 23 and arrived about an hour before posted opening time. Park opened gates half hour earlier than posted time (posted was 7, opened gates at 6:30). Because of the crowd, even though we were standing in line at 6, it took us until 7:05 to get in the gate.
Majority of it seemed to be to get boarding groups for ROTR.