When can a bank transfer actually be reversed, and why do banks say "it is gone" for some payments but not others?

The distinction is who initiated it, and once you see it the whole thing is predictable.

Pull payments. You give somebody permission to take money — a card payment, a direct debit. The mechanism is designed around the idea that the taker might be wrong or dishonest, so there is a built-in route to reverse it. Card schemes call it a chargeback; direct debit schemes have their own guarantee. The reversal is part of the product.

Push payments. You instruct your bank to send money — a bank transfer, an instant payment. The system is built to settle finally and quickly. There is no reversal mechanism because the whole design assumes you meant it. Once it lands in the recipient's account it is legally theirs, and the bank has no button.

Your two friends used one of each. The card dispute went through a process that exists. The transfer had no process to go through, which is what "it is gone" means — it is a statement about the rails, not about effort.

On question 2, a recall is not a reversal and the difference matters a lot.

When your bank attempts a recall, it sends a request to the receiving bank asking it to return the funds. The receiving bank then has to get the account holder's agreement, because that money is legally theirs. If they say no, or do not respond, nothing happens. If they have already moved it, there is nothing there to return even if they agree.

So the honest description is: your bank is asking a stranger, politely, via their bank, to give it back. Success depends almost entirely on whether the recipient is an honest person who received a mistake — in which case it usually works — or someone who took the money deliberately, in which case it almost never does.

That is why speed matters so much for transfers and barely at all for card disputes. With a card you are invoking a process. With a transfer you are racing the recipient.