Neither, it's just fairly clear to me that this is not the sort of feature that a third party client to a service can typically implement if there is no support

Neither, it's just fairly clear to me that this is not the sort of feature that a third party client to a service can typically implement if there is no support for it in the official client (completely separate from this being Twitter). As another example, Gmail has an "undo" button on sending an email, but other email clients don't (mostly). Why? Because email doesn't have the concept of un-doing a send, so the only way they can implement this at the "protocol level" is to... not, and to implement it entirely in the client with a delay.