There's no need to tell the EA anything other than the fact that a management company exists & to inform the buyer.
The EA doesn't need to be told anything about the supply or not of documentation.
When the seller's solicitor requests documentation they can be informed that it is the policy of the company only to supply documentation when accounts are clear. That could apply to people paying by dd as much as people in arrears.
People get very hot under the collar about data protection - less so, it sometimes seems about owners who refuse to pay what's owed.
Refusing to supply documentation is one of the few ways available to clear accounts in the event of a sale, without incurring a large cost.