It would be interesting to see some other reviews.
In this case the Aether folks did what they had to do and took the pax to the gate, but because the pilot wasn't there, they couldn't be boarded so were left in the corridor with everyone else.
Reviews of it pre-covid had you brought up the stairs and gate staff checking docs and boarding effectively as group 0.

Since for BA there are no steps to the plane but an air bridge instead, it's hard to see what else they could do.
Perhaps when the T2 move completes and everyone is bussed to the plane, this might work better.