The usual complaints are situations where BA has only contract staff and so find it difficult to react to a planeful of passengers. It's usually "it was chaos, there were no BA representatives available, there were passengers with young children and distressed elders, and no assistance with booking a hotel so we had to sleep on the floor". Thankfully at Heathrow there is plenty of staff and this situation is less likely unless there's a mass event.

Rebooking would have happened with or without the phone call. This is a part of BA IT that generally works. It usually proceeds in status order if there is limited capacity.

Opening a door in T3 is, well, opening a door in T3. It needs some staff availability, but there is a well defined route for leaving the terminal for passengers who don't travel. It's not going above and beyond. It's opening a door.

And hotels, you always have the choice of joining a queue of 150 people or booking yourself something. If anything BA would do better to stick a sign up "If you don't want to queue, here are our reimbursement rules". But in the absence of that, the disruption thread is a great resource and I always point punters in the vicinity at it if I have a disrupted flight. Some people prefer the voucher if nervous about reimbursement, but generally I'd have a booking set up and ready to go when a cancellation looks likely.

Disruption Assistance thread - signposts and what you need to know - 2025 edition - FlyerTalk Forums

I'm all for credit where credit is due, but there's nothing here that isn't what I would expect as standard at Heathrow. On the other hand I'm way more tolerant of lower standards at outstations.