I was practicing with 2 different phones today. Samsung galaxy s10, and and older Android Phone (Nextbit Robin).
I used the same strategy on each, in parallel. wait till exactly 8, click my Find out More, Join Boarding Group if Red, My status otherwise.
Each phone had a different result:
on the S10: after i hit Find out More, Join Boarding Group seemed grey but immediately turned Red, and went through fine.
on the NB: after i hit Find out More, Join Boarding Group was grey, i press My status. Join a Boarding Blue still didn't turn blue / clickable. tried a few refreshes and that didn't work. backed out to first step and tried again. same. backed out again and got through on third time. i imagine that would have been a backup at that point.
My explanation is either that the newer phone helped in refreshing quickly, or it was just luck that the older phone took a while to refresh that BGs are open. I can see from that experiment how people that are prepared, come to park, and are hit with a major disappointment. I'm preparing myself for such, but also getting 2 phones, and my wife's phone for a total of 3 to get a better chance.