My guess is that non-pools firms are not interested in trying to create an arrangement which is not contractual. That's because bookmakers may deal in very substantial stakes and may extend large amounts of credit to clients.The Gaming Act 2005 s334 changed the law. Before then a 'gambling debt' was not enforceable in the courts.The Act made a contract which was connected with gambling enforceable. I think William Hill and others, owed big sums, like to be able to sue the client ! Pools companies deal in small sums in bets, don't give credit much, if at all, and so won't worry about bad debts,.
Yes, Pools companies could decide not to pay you (just as Vernons refused Mr Jones) but it wouldn't be good for business if they did it often! So far as I'm aware their wording is still valid to make an 'honour only' arrangement.Your pools company seem to think so, as it still uses the wording. .