"TTT, reverse mortgage is a proper, recognised term meaning equity release." - is it really? first I've heard of it and it's wrong it is not the reverse of a mortgage it's a mortgage.
"There is no mortgage involved in saving up to buy a house outright " - yes it's like a reverse loan often prescribed for those with no credit, how much can you afford to pay each month? well save it until you have enough to buy what you want to buy. The reverse mortgage would be the same, ostensibly it is a loan and the opposite of a loan is saving, geddit?