I think people are misreading this.
There’s not much change to the rule for 3 or more aircraft in slots in AB sometimes giving you a 0.3 BR advantage (but see below). The bigger change seems to be if you choose to have only 1-2 aircraft in slots.
Before:
“If you want to send less than 3 vehicles into battle (specifically the number of serviceable aircraft in the crew slots is less than 3), so the BR values for the missing aircraft in the formula will be counted as A-0.6.”
Now:
"For 2 vehicles
If only two crews go into the battle (the number of usable aircraft in the crew slots is 2), then the calculation of the average BR uses the same principles but different formula:
BR = A/2+B/2
where A and B are the BRs of the vehicles in the crew slots.
"For 1 vehicle
If only one vehicle participates in the battle, then the average BR will be equal to its BR."
It’s the two-plane rule that seems the interesting change here.
Before if you took one plane into lineup you got a 0.3 BR offset (so a Sakeen at 3.3 with nothing else became a 3.0). That is apparently going away for the single plane. Before, if you only two planes, it also normally gave you that same 0.3 offset (so a 4.3 plus a 4.7 became a 4.3 lineup). Sounds like the one thing this would change would be if you took two planes, and if it’s a 4.3 plus a 3.7 or below, you’d still get the 4.0 lineup, but if you took two planes and it’s a 4.7 plus a 4.3, then it becomes a 4.7, same as the new single-plane situation? Guess we’ll find out in the morning.
Graphic of the old system that made sense to me, will wait to see the new one:
Spoiler

For 3+ vehicle lineups, it reads like(?) the exception for vehicles 2.0 BR or below changing the calculation could also be gone (note, that’s not for sure), which would make the new rule look like this, in the same format:
Spoiler
So before, if one of your vehicles was 2.0+ BR below it was ignored, so you ended up with the higher BR anyway. It appears that’s gone now (since it’s not in the new writeup, and that WOULD be a simplification), so if that exception is also gone you should be able to get that 0.3 BR bonus with a wider range of sub-BR vehicles in slots 2 and 3 than before. At least that’s my read.