DLA and the Benefits Cap

Re DLA and the benefits cap, the government’s impact assessment says that any household with someone claiming DLA will be exempt from the cap.

However, I am sure that I read (on Carers UK website I think) that this exemption does not apply if you are caring for a disabled child over the age of 18, who is the DLA recipient. Can you please advise if that is correct?

Also, if someone is caring for 3 disabled children, aged 9, 18 and 21, who are all in receipt of DLA, then am I correct in assuming that the cap will not apply and that the DWP should not have sent out a letter advising that it will?

Thanks for any help received.