I too remember there always being arrival times, which I read as "suggestions."
After the Cooties, they began enforcing not just broad arrival times like in the past, but more narrow windows, I believe they were initially a half hour (?) between each.
This was how it was for us on Horizon Sept 2021.
They were then and still are enforcing the times.
I would say this, if you got lucky and rolled up during a slow period, they MAY let you go ahead.