Thought I'd add a quick data point. We are flying EK772 departing @ 3:55. We arrived at DXB the day prior @ 15:45 to check in. Got to the e-gates just past 16:00 and the document checker mentioned we could only enter 8 hours prior to flight and would need to come back later. I acted surprised and mentioned I was told I could enter 12 hrs prior to flight. He again said sorry 8 hours prior, and asked if I had a reservation at airside hotel. I told him no, and I again said that I was told I could arrive 12 hours prior to departure. He seemed a bit frustrated, but said "go ahead and try'. We were at the egates just under 12 hours prior to departure and we're allowed through. So seems the "hard" 10 hour prior is not necessarily true and honestly might depend on the agent allowing pax to clear egates.

Either way glad we were able to enter and quickly made our way to the A First class lounge for dinner. Now off to the B gate lounge to enjoy the Moet Champagne bar.