The answer is in the letter. 
They don't want to deal with coinage so they don't want customers who collect coins during their business activities and then want to deposit them. My wife banks with Halifax and they won't exchange coins for her.
I'm with Santander for business.
But I don't trust them with cash after they blundered a couple of years ago.
I put all the cheques BACS into business account.
Cash (notes) pay in at the machine to put into my personal account then BACS it across to business account.
Coins, I don't get that much tbh, but I save them up. Probably only go to the actual lady ebbing the glass to pay them in twice or 3 times a year.
Been questioned a couple of times but never had any actual issue with it.